A new reaction of electron-rich thiophenemethanols

Abstract

3-Methoxythiophene-2-methanol 2 undergoes condensation with elimination of water and formaldehyde under acidic conditions to give bis(3-methoxy-2-thienyl)methane 3 and a further product resulting from reaction of 3 with the thienylmethyl carbocation; the other electron-rich thiophenemethanols 8 and 10 react similarly.

Synthesis and Optical and Electronic Properties of Thiophene Derivatives

“…Instead, we reduced the 2-acid-5-ester-thiophenes to the symmetric thiophene-2,5-dimethanols, shown as series 1. Related thiophene-2,5-dimethanols have been synthesized previously, [38][39][40] and the synthesis of 1b has been reported by Nakayama [41] and Chandra. [42] We gently oxidized series 1 using MnO 2 [43] to yield thiophene-2,5-dicarbaldehydes, series 2, in nearly quantitative yields.…”

Flash vacuum pyrolysis of oxo-stabilised phosphonium ylides containing methoxythiophene and methylthiophene groups

“…In contrast to the simple ylides which could be prepared in one step from a commercial phosphonium salt and a thiophene-containing acid chloride, the extended ylides required the methoxythiophene group to be located in the phosphonium salt and thus involved multi-stage synthesis (Scheme 10). As we noted some time ago [24], attempted lithium aluminium hydride reduction of methoxythiophene esters is not without complication. Any contact of compounds such as 23 with acid leads to oligomerisation so completely non-acidic conditions must be used.…”

“…This was prepared as in 2. 3. fluoreno [3,4-b]thiophene 39 (25%); δ H 3.82 (2H, s, CH 2 ); δ C 37.1 (CH 2 ); m/z 222 (M + , 90%), 189 (24), 176 (18), 150 (12), 110 (100), 98 (39) and 88 (40).…”

“…Any contact of compounds such as 23 with acid leads to oligomerisation so completely non-acidic conditions must be used. The readily available methyl 3-methoxythiophene-2-carboxylate [25] was thus reduced with a neutral/basic work-up [24] to give 23 and this was followed by combined chlorination and phosphonium salt formation, also under non-acidic conditions using Ph 3 P/CCl 4 . The resulting phosphonium salt 24 was then deprotonated and acylated with 0.5 equiv.…”

“…The ylide 29 with the isomeric structure was likewise prepared (Scheme 11) starting from methyl 4-methoxythiophene-3-carboxylate [20] by LiAlH 4 reduction under nonacidic conditions [24] to give 27, chlorination and phosphonium salt formation to give 28 followed by deprotonation and treatment with 0.5 equiv. cinnamoyl chloride.…”