figshare
Browse
jo962191n_si_001.pdf (915.59 kB)

Synthetic Applications of 3,4-Bis(trimethylsilyl)thiophene:  Unsymmetrically 3,4-Disubstituted Thiophenes and 3,4-Didehydrothiophene,

Download (915.59 kB)
journal contribution
posted on 1997-04-04, 00:00 authored by Xin-Shan Ye, Henry N. C. Wong
3,4-Bis(trimethylsilyl)thiophene (1a) 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 (1a) can function as a versatile building block for the construction of unsymmetrically 3,4-disubstituted thiophenes utilizing its stepwise regiospecific mono-ipso-substitution followed by palladium-catalyzed cross-coupling reactions. In this manner, thiophenes 15, 16, 17aj, 19a,b, 20, 22ac, 23a,b, 24ad, 25ac, and 27aj were prepared. The thiophene-3,4-diyl dimer 28 and thiophene-3,4-diyl tetramer 29 were also realized by palladium-catalyzed self-coupling reaction of organoboroxines. The stannylthiophene 31, formed by conversion of the C−Si bond to a C−Sn bond via boroxine 26c underwent both carbonylative coupling and lithiation followed by quenching with electrophiles to afford unsymmetrically 3,4-disubstituted thiophenes 33 and 36ac as well. Moreover, 3,4-bis(trimethylsilyl)thiophene (1a) can be used as the starting material for the generation of the highly strained cyclic cumulene 3,4-didehydrothiophene (2), whose existence was substantiated by its trapping reaction with several alkenes.

History