Synthetic Applications of 3,4-Bis(trimethylsilyl)thiophene:
Unsymmetrically 3,4-Disubstituted Thiophenes and
3,4-Didehydrothiophene<sup>†</sup><sup>,</sup><sup>‡</sup>
Xin-Shan Ye
Henry N. C. Wong
10.1021/jo962191n.s001
https://acs.figshare.com/articles/journal_contribution/Synthetic_Applications_of_3_4-Bis_trimethylsilyl_thiophene_Unsymmetrically_3_4-Disubstituted_Thiophenes_and_3_4-Didehydrothiophene_sup_sup_sup_sup_sup_sup_/3705210
3,4-Bis(trimethylsilyl)thiophene (<b>1a</b>) was
synthesized by three routes: (a) 1,3-dipolar
cycloaddition;
(b) modification of 3,4-dibromothiophene; and (c) intermolecular
thiazole−alkyne Diels−Alder
reaction. 3,4-Bis(trimethylsilyl)thiophene
(<b>1a</b>) can function as a versatile building block for
the
construction of unsymmetrically 3,4-disubstituted thiophenes utilizing
its stepwise regiospecific
mono-<i>ipso</i>-substitution followed by palladium-catalyzed
cross-coupling reactions. In this manner,
thiophenes <b>15</b>, <b>16</b>,
<b>17a</b><b>−</b><b>j</b>, <b>19a,b</b>,
<b>20</b>, <b>22a</b><b>−</b><b>c</b>,
<b>23a,b</b>, <b>24a</b><b>−</b><b>d</b>,
<b>25a</b><b>−</b><b>c</b>, and
<b>27a</b><b>−</b><b>j</b> were prepared.
The thiophene-3,4-diyl dimer <b>28</b> and thiophene-3,4-diyl
tetramer <b>29</b> were also realized by palladium-catalyzed self-coupling reaction of organoboroxines. The
stannylthiophene <b>31</b>, formed by conversion
of the C−Si bond to a C−Sn bond <i>via</i> boroxine
<b>26c</b> underwent both carbonylative coupling and
lithiation followed by quenching with electrophiles to afford
unsymmetrically 3,4-disubstituted
thiophenes <b>33</b> and <b>36a</b><b>−</b><b>c</b>
as well. Moreover, 3,4-bis(trimethylsilyl)thiophene
(<b>1a</b>) can be used as
the starting material for the generation of the highly strained cyclic
cumulene 3,4-didehydrothiophene (<b>2</b>), whose existence was substantiated by its
trapping reaction with several alkenes.
1997-04-04 00:00:00
Bis
thiophenes 15
unsymmetrically
bond
boroxine 26 c
Synthetic Applications
stannylthiophene 31
building block
disubstituted