A yne-Based Syn hesis o Cyclobu adiene-Con aining Oligoacenes
and Rela ed Ex ended Biphenylene De i a i es
Be a Ál a ez,a, b Jesús Janei o,a, b Agus ín Cobas,bManuel A. O uño,a
Diego Peña,a, b En ique Gui ián,a, b and Dolo es Pé eza, b,*
a
Cen o Singula de In es igación en Química Biolóxica e Ma e iais Molecula es (CiQUS), Uni e sidade de San iago de
Compos ela. 15782-San iago de Compos ela, Spain
Phone: +34 881815783
E-mail: [email p o ec ed]
b
Depa amen o de Química O gánica, Uni e sidade de San iago de Compos ela. 15782-San iago de Compos ela, Spain
Manusc ip ecei ed: No embe 2, 2023; Re ised manusc ip ecei ed: Janua y 7, 2024;
Ve sion o eco d online: Feb ua 2, 2024
Dedica ed o P o . Miquel A. Pe icàs, wi h deep admi a ion o his excep ional ca ee and ou s anding con ibu ions, including he
es ablishmen o he Ins i u Ca alà d’In es igació Química (ICIQ)
Suppo ing in o ma ion o his a icle is a ailable on he WWW unde h ps://doi.o g/10.1002/adsc.202301264
© 2024 The Au ho s. Ad anced Syn hesis & Ca alysis published by Wiley-VCH GmbH. This is an open access a icle unde he
e ms o he C ea i e Commons A ibu ion Non-Comme cial NoDe i s License, which pe mi s use and dis ibu ion in any
medium, p o ided he o iginal wo k is p ope ly ci ed, he use is non-comme cial and no modi ica ions o adap a ions a e made.
Abs ac : A p e iously undesc ibed a yne de i ed om a π-ex ended biphenylene, 2,3-
didehyd obenzo[b]biphenylene, has been de eloped. The pa icipa ion o his new a yne building block in [4+
2] and palladium-ca alyzed [2+2+2] cycloaddi ion eac ions has been applied o he syn hesis o a a ie y o
polycyclic conjuga ed hyd oca bons (PCHs) wi h appealing s uc u es which combine (a oma ic) benzene and
(an ia oma ic) cyclobu adiene (CBD) ings. Among hem, a amily o unsubs i u ed (o ba ely subs i u ed)
CBD-oligoacenes has been accessed by i e a i e Diels-Alde eac ions o he new a yne wi h u ans and/o
isobenzo u ans, ollowed by deoxygena i e a oma iza ion o he esul ing epoxy-de i a i es. The expe imen al
and compu a ional s udies o he newly syn hesized PCHs sugges an impo an deg ee o elec on
delocaliza ion along he polycyclic skele on, mo e p onounced in he linea ly used de i a i es. The compu ed
ACID plo s e eal clockwise cu en densi y ec o s a he pe iphe al bonds, o igina ing om he σ
con ibu ions o he an ia oma ic cyclobu adiene ings.
Keywo ds: Polycyclic conjuga ed hyd oca bons; A ynes; Cycloaddi ion eac ions; Biphenylene; Cyclobu adiene-
con aining oligoacenes
In oduc ion
Polycyclic π-conjuga ed hyd oca bons (PCHs) ha e
a ac ed wide a en ion om he scien i ic communi y
due o hei p ominen ole as o ganic semiconduc o s
and elec oac i e ma e ials o he de elopmen o
o ganic elec onics.[1] Linea ly used igid sys ems,
such as acenes, a e conside ed pa adigma ic o ganic
semiconduc o s,[2] bu hei gene al use is hampe ed by
he dec eased chemical s abili y associa ed o he
ex ension o he leng h o he acene, a ea u e ha can
be quali a i ely explained on he basis o Cla ’s π-
sex e ule.[3] Angula ly used phenes, s a phenes[4] and
o he ben -shaped oligoacene de i a i es[5] a e also
p omising op oelec onic ma e ials. Among he di e se
amilies o PCHs, hose con aining used ou -mem-
be ed cyclobu adienoid ings a e pa icula ly in e es -
ing due o he p ope ies associa ed wi h he al e na ion
o a oma ic and an ia oma ic ing cu en s in hei
s uc u es. In his con ex , in addi ion o he ascina ing
linea , angula and helical [N]phenylenes,[6] p o usely
s udied by Vollha d and co-wo ke s[7] among o he s,
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ecen in e es has a oused on he s udy o o he
polycyclic sys ems, including linea phenylene-con-
aining oligoacenes[8,9] and he e oacenes,[10] de i a i es
wi h non-linea polycyclic a oma ic moie ies[11] o
isome ic g aphene nanos uc u es o med by used
biphenylene uni s.[12] Biphenylene-con aining PCHs
ha e been ecen ly explo ed o single-molecule
junc ions,[13] o as po en ial single ission
ch omopho es,[14] while he e ec o he cyclobu a-
diene ings on Bai d a oma ici y and i s in luence in
he iple s a e ene gies o he esul ing π-ex ended
de i a i es[15] ha e also been s udied. Con e sion o
PCHs con aining cyclobu adiene (CBD) ings in o
con o ed benzenoid conjuga ed hyd oca bons h ough
me al-ca alyzed CC bond ac i a ion has also been
ecen ly desc ibed.[16]
Some yea s ago, we applied ou ecen ly disco e ed
palladium-ca alyzed [2+2+2] cycloaddi ion o
a ynes[17] o he syn hesis o is-
(benzocyclobu adiene) iphenylene.[18] Mo e ecen ly,
we used his biphenylene ime as a p obe o he si e-
selec i e co alen unc ionaliza ion o a semi-conduc-
o su ace.[19] Ou enewed in e es in PCHs con aining
ou -membe ed ings led us o plan he syn hesis o π-
ex ended de i a i es, including CBD-con aining oli-
goacenes, by means o cycloaddi ion eac ions o a
benzobiphenylene-based a yne building block, 2,3-
didehyd obenzo[b]biphenylene (1), accessed om i s
Kobayashi- ype a yne p ecu so [20] 2(Scheme 1). He e
we epo he esul s o ou syn he ic s udy, and he
p elimina y e alua ion o he elec onic p ope ies and
a oma ic cha ac e o he newly syn hesized CBD-
con aining PCHs.
Resul s and Discussion
The syn hesis o 3-( ime hylsilyl)benzo[b]-bipheny-
lene-2-yl i la e (2) was achie ed h ough he wo
al e na i e ou es depic ed in Scheme 2, bo h based in
he cons uc ion o he 2,3-disubs i u ed
benzo[b]biphenylene co e by means o a cobal (I)-
ca alyzed [2+2+2] cycloaddi ion o 2,3-die hynyl-
naph halene (3) wi h an app op ia e alkyne. Thus,
eac ion o 3wi h bis( ime hylsilyl)ace ylene
(BTMSA, used as co-sol en ) in he p esence o
CpCo(CO)2, unde hea ing and i adia ion, p o ided
2,3-bis( ime hylsilyl)benzo[b]biphenylene (4)[21] in a
sa is ac o y 90% yield. Fo he ans o ma ion o 4in o
i la e 2, i s we a emp ed he p o ocol p e iously
de eloped o he syn hesis o an analogous bipheny-
lyne p ecu so ,[18] which allowed he isola ion o 2in
low yields and wi h sca ce ep oducibili y. Be e
esul s we e ob ained when 4was subjec ed o a double
b omodesilyla ion ollowed by nucleophilic subs i u-
ion o one o he b omine a oms by me hoxide o yield
5. Subsequen ea men wi h BB 3a o ded an
uns able o-b omophenol, which was di ec ly subjec ed
o he p o ocol de eloped in ou g oup o he syn hesis
o o-( ime hylsilyl)a yl i la es[22] o gi e 2( ou e A
in Scheme 2; six s eps and 20.7% yield om 3).
Al e na i ely, he Co(I)-ca alyzed [2+2+2] cyclo-
addi ion o 3wi h he alkynylbo ona e 6[23] a o ded 7
in 40% yield. The ipso-hyd oxyla ion o he a ylbo -
onic es e wi h sodium pe bo a e, ollowed by i la ion
o he esul ing phenol, allowed he s aigh o wa d
syn hesis o 2in 68% yield ( ou e B in Scheme 2; h ee
s eps and 27.2% o e all yield om 3).
The e iciency o 2as p ecu so o
benzo[b]biphenylyne 1was e alua ed by means o
apping expe imen s wi h ypical dienes, such as
u ans and cyclopen adienones (Scheme 3). In pa ic-
ula , ea men o 2wi h CsF in he p esence o excess
u an (o 2,5-dime hyl u an) success ully a o ded he
co esponding [4+2] adduc s 8a[24] and 8 b in 90%
and 89% isola ed yields, espec i ely. On he o he
hand, he eac ion o 2wi h he polycyclic cyclo-
pen adienone 9[25] unde a yne- o ming condi ions
ollowed by hea ing o he esul ing adduc 10 in
e luxing 1,1,2,2- e achlo oe hane allowed he isola-
ion o 11 in an excellen 94% yield, as he esul o a
Diels-Alde eac ion be ween a yne 1and diene 9, and
subsequen chele opic ex usion o CO.
Scheme 1. 2,3-Didehyd obenzo[b]biphenylene (1) and i s Ko-
bayashi- ype a yne p ecu so 2.
Scheme 2. Syn hesis o 3-( ime hylsilyl)-benzo[b]biphenylene-
2-yl i la e (2) [HMDS=hexame hyldisylazane; PBS=sodium
pe bo a e].
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Nex , we es ed he pe o mance o 1unde he
condi ions de eloped by ou g oup o palladium-
ca alyzed [2+2+2] cycloaddi ion eac ions o
a ynes.[4b,17] Thus, ea men o 2wi h CsF in he
p esence o ca aly ic amoun s o Pd(PPh3)4 esul ed in
he o ma ion o a yellow solid, sca cely soluble in
common o ganic sol en s, which was iden i ied as he
cyclobu adiene-con aining s a phene 12 on he basis o
i s high esolu ion mass spec um (Scheme 4). When
he eac ion was pe o med in he p esence o dime hyl
ace ylene dica boxyla e (DMAD), compound 13 was
isola ed in a 79% yield, as he esul o a [2+2+2]
cycloaddi ion be ween wo molecules o a yne 1and
one o he elec on-de icien alkyne. In acco dance o
p e ious esul s wi h o he a ynes,[17b,26] he use o
Pd2(dba)3as he ca alys esul ed in he selec i e
o ma ion o dibenzobiphenylene 14 by means o he
eac ion o one molecule o he a yne and wo o he
alkyne (Scheme 4).
Once p o ed he e iciency o i la e 2as p ecu so
o 2,3-didehyd obenzo[b]biphenylene (1), and he
u ili y o his no el a yne o he easy access o π-
ex ended cyclobu adiene-con aining polycyclic conju-
ga ed sys ems, we decided o explo e he use o his
building block o he syn hesis o oligoacene de i a-
i es inco po a ing cyclobu adiene ings (CBD-oligoa-
cenes). Elegan syn he ic s a egies ecen ly de eloped
by Swage ,[8a,b] Xia,[8c,d] Miao[8 ] o G ibble[24] ha e
allowed he access o CBD-oligoacenes unc ionalized
wi h la ge phenyl, alkyl and/o ( ialkylsilyl)e hynyl
subs i uen s, as analogues o acenes in which he
p esence o ou -membe ed ings in o he linea π-
backbone inc eases he numbe o Cla sex e s,
esul ing in highe s abili y. The in luence o he
subs i uen s in he molecula packing and elec onic
p ope ies has been illus a ed by some high-mobili y
de i a i es,[8d,e] while he e ec o he ex ension and
(an i)a oma ici y o he polycyclic conjuga ed co e in
cha ge anspo has also been heo e ically s udied.[27]
Wi h hose p eceden s in mind, and on he basis o ou
own wo k in he syn hesis o long acenes,[28] we
decided o app oach he cons uc ion o unsubs i u ed
(o ba ely subs i u ed) CBD-oligoacenes om adequa e
endoxide-p ecu so s, which would be accessed by
i e a i e Diels-Alde eac ions be ween biphenylene-
based a ynes and u ans (o isobenzo u ans).
The highly eac i e isobenzo u ans Icould be
easily gene a ed by gen le wa ming o epoxyacenes II,
ob ained by eac ion o a ynes III wi h u ans, in he
p esence o 3,6-bis(py idyl)-1,2,4,5- e azine
(BPTZ)[29] (Figu e 1). This app oach was used in his
wo k o accessing isobenzo u an (15a) and de i a-
i es 15b,15c,16,17 a and 17b.
As a p oo o concep o ou app oach we i s
s udied he eac ion o biphenylyne 18, whose gen-
Scheme 3. T apping o 2,3-didehyd obenzo[b]biphenylene (1)
gene a ed om o-silyla yl i la e 2.
Scheme 4. Palladium(0)-ca alyzed [2+2+2] cycloaddi ion eac ions o 2,3-didehyd obenzo[b]biphenylene (1).
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e a ion om i la e 19 had been p e iously epo ed
by ou g oup,[18] wi h isobenzo u an 16 ob ained om
endoxyde 20. The eac ion a o ded he epoxy-de i a-
i e 21 in a sa is ac o y 74% yield. Deoxygena i e
a oma iza ion o 21 was success ully achie ed by
ea men wi h ca aly ic amoun s o ammonium
pe hena e in he p esence o iphenylphosphi e as
oxygen sca enge ,[30] a o ding 22 as a whi e, highly
insoluble solid in 70% yield (Scheme 5). The iden i y
o 22 was deduced on he basis o i s HRMS and UV-
is spec a (see SI), being diagnos ic he ed shi o
he lowes ene gy abso p ion band o 22 (λmax =
451 nm) wi h espec o ha o 21 (λmax =388 nm). The
low solubili y o 22 p ecluded he analysis by 1H
NMR.
Nex , we s udied he cycloaddi ion o benzo[b]bi-
phenylyne (1) gene a ed by luo ide-induced decom-
posi ion o i la e 2, wi h in si u gene a ed isobenzo-
u ans 15,16 and 17, ob aining he expec ed cyclo-
adduc s 23–25 in sa is ac o y yields, anging om 42%
o 23b o 73% o 23a (Scheme 6), as pe ec ly s able
and soluble p oduc s which could be ully cha ac e -
ized. The deoxygena i e a oma iza ion o 23–25 was
success ully pe o med by henium-ca alyzed p oce-
du e men ioned abo e o by ea men wi h HCl and
iP OH (e ec i e o he dime hyl-subs i u ed 25b), o
a o d he expec ed CBD-oligoacenes 26–28 in good
yields (Scheme 6). Rema kably, he cyclopen ene-
used de i a i e 26c esul ed soluble enough o
success ully ob ain i s 1H NMR spec um in 1,1,2,2-
e achlo oe hane-d2. Wi h ega d o he o he newly
syn hesized CBD-oligoacenes, al hough he lack o
solubili y p ecluded hei cha ac e iza ion by NMR,
hei iden i y was con i med by high esolu ion mass
spec ome y and analysis o hei UV- is spec a. In
pa icula , compounds such as 26a–co 28a–b
displayed simila spec a ha hose epo ed o
p e iously desc ibed alkynyl o a yl-subs i u ed
analogues.[8]
Selec ed expe imen al da a p o ided by he UV- is
and luo escence spec a o he newly syn hesized
Figu e 1. Isobenzo u an building blocks used in his wo k.
Scheme 5. Syn hesis o bis(benzocyclobu a)an h acene 22 by
i e a i e Diels-Alde eac ions o biphenylyne (18) [BPTZ=
3,6-bis(py idyl)-1,2,4,5- e azine].
Scheme 6. Syn hesis o cyclobu adiene-con aining oligoacenes 26–28 by cycloaddi ion eac ions o 2,3-
didehyd obenzo[b]biphenylene (1); see SI o de ails.
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cyclobu adiene-con aining PCHs a e summa ized in
Table 1, oge he wi h he esul s o he compu a ional
es ima ion o he ene gy gaps (see SI o ull de ails).
The spec a o he [2+2+2] cycloadduc s 12–14
show lowes ene gy abso p ions in he ange o 421
( o 14) o 448 ( o 13) nm. Wi h ega d o he linea ly
used de i a i es, i is wo h o no e ha while all he
epoxy-oligoacenes 23–25 exhibi almos iden ical low-
es ene gy abso p ions a ound 405–410 nm, associa ed
o he benzo[b]biphenylene ch omopho e, he co e-
sponding deoxygena ed CBD-oligoacenes show la ge
λmax alues (see Figu e 2a, o 25b/28 b). The wa e-
leng h o hese lowes abso p ions inc eases wi h he
size o he linea polycyclic sys em, om λmax
�440 nm o 26, o 479 nm o 28 b. In all cases, he
abso p ion is also signi ican ly ed-shi ed wi h espec
o ha o an h acene (λmax =373 nm), he la ges
polycyclic benzenoid ch omopho e con ained in each
o he s uc u es, demons a ing an impo an deg ee o
elec on delocaliza ion along he polycyclic skele on
despi e he p esence o he an ia oma ic cyclobu adiene
moie ies. Compa ison o he spec a o he angula ly
shaped 13 wi h he linea analogues o simila size 28
sugges s ha he elec on delocaliza ion is mo e
signi ican in he la e .
Wi h ega d o he luo escence, i is ema kable he
e y small S okes shi s obse ed in he linea CBD-
oligoacenes, anging om 0 o 2 nm, which is
indica i e o he igid s uc u e o hese compounds.
As ano he in e es ing ea u e, he luo escence spec a
o solid 28a and 28b exhibi la ge ba hoch omic shi s
wi h espec o measu emen s in solu ion (146 and
119 nm, espec i ely; see Figu e 2b o 28 b), ha a e
signi ican ly la ge han hose obse ed o he same
polycyclic sys ems p o ided wi h pendan phenyl and
TIPS-e hynyl g oups[8a] and may cons i u e a p elimi-
na y e idence o e ec i e elec onic coupling be ween
neighbou ing molecules in he solid s a e.[31]
The s uc u es and p ope ies o he newly syn he-
sized compounds we e also compu a ionally s udied.
Op ical gaps we e calcula ed by TDDFT using he
B3LYP and O3LYP densi y unc ionals wi h he 6–311
+ +G(d,p) basis se (see Table S1). While he B3LYP
calcula ed gaps esul ed, as expec ed, sligh ly o e -
es ima ed, he use o O3LYP, which is simila o
B3LYP bu wi h a smalle pe cen age o exac HF,
p edic s smalle ene gy gaps ha a e in excellen
ag eemen wi h he expe imen al alues (wi hin 0.2 eV
o all compounds analyzed, see Tables 1 and S1).
Nex , we s udied he local and global a oma ici y/
an ia oma ici y o he newly syn hesized CBD-PCHs
by NICS-XY scan calcula ions,[32] using he σ-only
me hod[33] a he GIAO-B3LYP/6-311+G(d) le el o
heo y (see SI o de ails). In all compounds, posi i e
NICS alues we e obse ed o he ou -membe ed
ings, indica ing hei an ia oma ic cha ac e . The pa a-
Table 1. Spec oscopic p ope ies[a] and Egap es ima ion o he
new CBD-con aining PCHs.
Comp. λmax
(nm)
λonse
(nm)
λem
(nm)
Egap(op )[c]
(eV)
Egap(calc)[d]
(eV)
11 459 465 464 (505)b) 2.67 2.67
12 437 455 468 2.73 2.67
13 448 455 455 2.73 2.75
14 421 427 428 2.90 3.09
22 451 460 451 2.70 2.82
26a 433 441 468 2.80 2.79
26b 440 445 441 2.79 2.77
26c 436 440 441 2.81 2.75
27 458 473 459 2.62 2.73
28a 470 475 470 (599)[b] 2.60 2.67
28b 479 490 480 (616)[b] 2.53 2.54
[a] Measu ed in 1,2,4- ichlo obenzene, excep he spec a o
11,13,14 and 26 a, measu ed in CHCl3.
[b] Measu ed in he solid s a e by means o an in eg a ing
sphe e.
[c] Egap(op ) =1241/λonse .
[d] Calcula ed a he TDDFT/O3LYP/6-311+G(d,p) le el.
Figu e 2. a) O e lay o he abso bance spec a o p ecu so 25 b
(in CHCl3) and CBD-oligoacene 28b (in 1,2,4- ichlo oben-
zene). b) Abso bance and luo escence spec a o 28b in
solu ion, and luo escence in he solid s a e.
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opici y o he cyclobu adiene ings is mo e p o-
nounced o compound 22 (NICS=6 ppm), wi h single
benzene ings used o he CBD a he PCH e mini,
and o he angula ly- used sys ems 12 and 13 (NICS
�5.5 ppm), while he bis(naph hocyclobu a)an h acene
ing sys em 28, p e iously s udied by Xia and co-
wo ke s,[8c] p esen s peak NICS alues o 3.9 ppm ( o
28a). On he o he hand, he a oma ic cha ac e o he
di e en benzenoid ings in each PCH s uc u e is
a ec ed by he p esence o he an ia oma ic cyclo-
bu adienoids and he associa ed bond localiza ion. To
illus a e his ea u e, Figu e 3 shows he NICS-XY
scans o he 9- ing polycyclic sys ems o 12,13a and
28a, showing he e minal benzenoid ings as he less
a ec ed (mo e a oma ic cha ac e ), he ings di ec ly
a ached o he CBDs as he less a oma ic, and a
signi ican di e ence in he a oma ic cha ac e o he
cen al ing o he polycyclic sys ems, being ha o he
linea ly- used CBD-oligoacene 28a he mos a oma ic.
Finally, o isualize he local dia opic and pa a-
opic ing cu en s induced by local a oma ici y and
an ia oma ici y, we compu ed he aniso opy o he
induced cu en densi y (ACID).[34] As a ep esen a i e
example, Figu e 4a shows he ACID plo o 28a;
whe e clockwise cu en densi y ec o s indica e
a oma ici y (black a ows) and an i-clockwise ones
desc ibe an i-a oma ici y ( ed a ows). As expec ed,
benzene uni s show clockwise ing cu en s, while
an i-clockwise ing cu en s a e obse ed in he cyclo-
bu adiene ings. Howe e , aking a close look a he
la e in Figu e 4b, one can see he p esence o
clockwise cu en densi y ec o s on he pe iphe al
bonds o he ou -membe ed ings, sugges ing a global
dia opic cu en loop ha ounds he whole sys em.
Figu e 4c shows ha hese clockwise ec o s come
Figu e 3. NICS-XY scans a he B3LYP/6–311+G(d) le el o
12,13a and 28 a.
Figu e 4. a) ACID plo o 28 a a isosu ace alue o 0.04. b) Zoom in on he cyclobu adiene uni . c) Con ibu ions om π- and σ-
ype o bi als.
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om he con ibu ions o he σ sys em. The o he
s udied compounds p esen simila ea u es, and hei
ACID plo s can be consul ed in Figu e S3 (SI).
Conclusion
In conclusion, we ha e syn hesized a amily o
ex ended cyclobu adiene-con aining PCHs wi h di e se
s uc u es, by means o e icien [4+2] o palladium-
ca alyzed [2+2+2] cycloaddi ion eac ions o a no el
a yne building block de i ed om
benzo[b]biphenylene. The se o ex ended phenylenes
syn hesized include CBD-oligoacenes (wi h up o nine
linea ly- used ings), angula ly- used analogues and a
s a -shaped benzobiphenylene ime . Ou app oach
allowed he syn hesis o s able, unsubs i u ed (o ba ely
subs i u ed) CBD-oligoacenes, which acco ding o
p elimina y examina ion o hei emission spec a
migh display e ec i e elec onic coupling in he solid
s a e, as unsubs i u ed acenes do. Expe imen al and
compu a ional s udies on he whole se ies o newly
syn hesized sys ems e eal an impo an deg ee o
elec on delocaliza ion along he polycyclic skele ons
despi e he p esence o he an ia oma ic cyclobu adiene
ings, wi h mo e p onounced delocaliza ion obse ed
in he linea ly used CBD-oligoacenes. The cu en
densi y plo ed on o he ACID isosu ace indica es a
complex pa e n o cu en s ha un eils he p esence
o clockwise pe iphe ical cu en o igina ing om he
σ con ibu ions o he ou -membe ed ings, hus
p o iding new insigh s in o he a oma ic and an ia -
oma ic in e ac ions wi hin hese in iguing molecula
a chi ec u es.
Expe imen al Sec ion
Selec ed Expe imen al P ocedu es
T ime hyl[3-(4,4,5,5- e ame hyl-1,3,2-dioxabo olan-
2-yl)benzo[b]biphenylen-2-yl]silane (7)
A solu ion o 2,3-die hynylnaph halene (160 mg, 0.91 mmol),
CpCo(CO)2(35 mL, 0.23 mmol) and ime hyl[(4,4,5,5-
e ame hyl-1,3,2-dioxabo olan-2-yl)e hynyl]silane (6, 200 mg,
0.91 mmol), in a mix u e o xylene (8 mL) and THF (3.5 mL),
was slowly added (3 h, sy inge pump) o a boiling solu ion o 6
(720 mg, 3,21 mmol) in xylene (12 mL). Ligh om a p ojec o
lamp (300 W, 50% o i s powe ) was di ec ed a he eac ion
mix u e du ing he addi ion. A e e luxing and i adia ion o
he mix u e o one addi ional hou , he sol en s we e emo ed
unde acuum. The c ude esidue was pu i ied by column
ch oma og aphy on silica gel (hexane/CH2Cl2, 4:2) o yield
ime hyl[3-(4,4,5,5- e ame hyl-1,3,2-dioxabo olan-2-
yl)benzo[b]biphenylen-2-yl]silane 7as o ange solid (130 mg,
35%).
3-(T ime hylsilyl)benzo[b]biphenylene-2-yl T i luo o-
me hanesul ona e (2)
A solu ion o ime hyl[3-(4,4,5,5- e ame hyl-1,3,2-dioxabo o-
lan-2-yl)benzo[b]biphenylen-2-yl]silane (7, 20 mg, 0.05 mmol)
in THF (2 mL) was added o a solu ion o sodium pe bo a e
(PBS, 38 mg, 0.25 mmol) in H2O (2 mL). A e s i ing a oom
empe a u e o 1 h, he eac ion mix u e was ex ac ed wi h
CH2Cl2(3×5 mL), he combined o ganic laye s we e d ied wi h
Na2SO4, il e ed and concen a ed unde educed p essu e. The
c ude esidue was used in he nex s ep wi hou any u he
pu i ica ion. The esidue was dissol ed in d y CH2Cl2(2.3 mL)
and o he esul ing solu ion, kep a 78°C, eshly des illed i-
P 2NE (14 mL, 0.08 mmol) and T 2O (17 mL, 0.10 mmol) we e
successi ely added. A e s i ing o 1 h a 78°C, he eac ion
mix u e was allowed o each oom empe a u e and s i ed o
2 h. The eac ion mix u e was quenched wi h aqueous NaHCO3
(sa u a ed solu ion, 2 mL), he phases we e sepa a ed and he
o ganic laye was ex ac ed wi h CH2Cl2(2×10 mL). The
combined o ganic laye s we e d ied wi h Na2SO4, il e ed and
concen a ed unde educed p essu e. The c ude was pu i ied by
column ch oma og aphy on silica gel (hexane/CH2Cl2, 4:2)
yielding i la e 2as a pale yellow solid (15 mg, 68%).
T is(naph hocyclobu a) iphenylene (12)
To a solu ion o 2(50 mg, 0.12 mmol) and Pd(PPh3)4(12 mg,
0.01 mmol) in d y CH3CN (3.5 mL), placed in a Schlenk lask
unde a gon, anhyd ous CsF (60 mg, 0.4 mmol) was added. The
eac ion mix u e was s i ed a oom empe a u e o o e 14 h.
The esul ing suspension was concen a ed unde educed
p essu e, he solid was collec ed by cen i uga ion subjec ed o
sonica ion-assis ed washing wi h po ions o CH3CN (2×2 mL),
H2O (2 mL), CH3OH (2×2 mL), E 2O (2×2 mL) and CH2Cl2
(2×2 mL), and d ied unde acuum o a o d 12 as a yellow
powde (14 mg, 58%).
Gene al P ocedu e o he Syn hesis o Oligoacene
Endoxides 21, 23–25
A solu ion o epoxyacene II and 3,6-bis(py idin-2-yl)-1,2,4,5-
e azine (BPTZ) in CH2Cl2, was s i ed a 45°C un il comple e
consump ion o he s a ing ma e ial (TLC moni o ing), gene a -
ing in si u he co esponding isobenzo u an I(15–17). To his
solu ion, kep a oom empe a u e in a Schlenk lask, a solu ion
o he p ecu so o a yne (2o 19, 1 equi .) in CH3CN was
added, ollowed by inely powde ed, anhyd ous CsF (5–
10 equi .; addi ion o he solid unde a posi i e low o a gon).
The mix u e was s i ed a oom empe a u e o 14 h, hen he
sol en was e apo a ed unde educed p essu e and he desi ed
endoxide was isola ed ei he by quick ch oma og aphy in silica
gel ( o 21,23a,23 b and 23c) o by cen i uga ion and
epea ed washing wi h di e en sol en s ( o 24,25a and 25b).
Gene al P ocedu e o he Deoxygena i e A oma iza-
ion o Endoxides 21, 23–25
Me hod A[39]
A solu ion o he oligoacene endoxide in a iP OH/CHCl3/HCl
(37%) mix u e was hea ed a 80°C o 24 h. Then, he eac ion
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mix u e was cooled o oom empe a u e, washed wi h NaHCO3
sa u a ed solu ion, and ex ac ed wi h CHCl3. The combined
o ganic laye s we e concen a ed unde educed p essu e, he
solid was collec ed by cen i uga ion, subjec ed o sonica ion-
assis ed washing wi h CH2Cl2, CH3OH and E 2O, and d ied
unde acuum o a o d he a oma ized p oduc .
Me hod B
A lame-d ied lask is cha ged wi h NH4ReO4, P(OPh)3and d y
oluene. A e s i ing o 20 min, he co esponding endoxide
was added and he esul ing mix u e was s i ed o 14 h. Then,
he sol en was concen a ed unde educed p essu e, he solid
was collec ed by cen i uga ion, subjec ed o sonica ion-assis ed
washing wi h po ions o CH2Cl2, H2O, CH3OH, CH2Cl2, and
d ied unde acuum o a o d he co esponding a oma ic
p oduc .
Acknowledgemen s
Financial suppo om g an s PID2019-110037GB-I00,
PID2022-140845OB-C62 and PID2022-139933NB-I00, unded
by MCIN/AEI/10.13039/501100011033, he Eu opean Union’s
Ho izon 2020 (FET-Open p ojec SPRING, G an No. 863098),
and ERC Syne gy G an MOLDAM (951519), he Xun a de
Galicia (ED431C 2020/22, ED431H 2020/21 and Cen o
singula de in es igación de Galicia acc edi a ion 2019–2022,
ED431G 2019/03) and he Eu opean Union (Eu opean Region-
al De elopmen Fund-ERDF) is g a e ully acknowledged. The
au ho s hank he Cen o de Supe compu ación de Galicia
(CESGA) o gene ous alloca ion o compu e ime. BA and JJ
hank he Agencia Es a al de In es igación o he awa d o
p e-doc o al ellowships (BES-2017-079748 and PRE2020-
092897, espec i ely).
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