Studies on silyl furans. II. Halodesilylation of 2‐trimethylsilyl‐3,4‐bis(methoxycarbonyl)furans

Abstract

Reactions of 2‐trimethylsilyl‐3,4‐bis(methoxycarbonyl)furans 1a,b with sulfuryl chloride, bromine, and iodine monochloride in acetonitrile afforded the corresponding 2‐halo‐3,4‐bis(methoxycarbonyl)furans 2a‐f via chloro‐, bromo‐, and iododesilylation in good yields, respectively. However, the reaction of 1a with bromine in carbon tetrachloride mainly gave 2‐bromo‐ 2b and 2‐bromo‐5‐trimethylsilyl‐3,4‐bis(methoxycarbonyl)furan (3) in 37% and 45% yields. Similarly, the reaction of 1a with iodine monochloride afforded 1a, 2‐chloro‐ 2a and 2‐iodo‐3,4‐bis(methoxycarbonyl)furan (2c) in 50%, 27%, and 23% yield.

Thieno-, Furo-, and Selenopheno[3,4-c]pyrrole-4,6-dione Copolymers: Effect of the Heteroatom on the Electrooptical Properties

“…Dimethyl 2,5-dibromofuran-3,4-dicarboxylate ( 8 ) was prepared from furan in three steps according to reported procedures (see Supporting Information). Saponification of compound 8 led to 2,5-dibromo-furan-3,4-dicarboxylic acid ( 9 ) (Scheme ). Treatment of compound 9 with oxalyl chloride gave 2,5-dibromo-furan-3,4-dicarbonyl dichloride ( 10 ).…”

“…Thiophene-3,4-dicarboxylic acid ( 1 ) was purchased from Frontier Scientific Inc. Dimethyl furan-3,4-dicarboxylate ( 4 ) was purchased from Aldrich. Thieno[3,4- c ]pyrrole-4,6-dione comonomers ( 2a–c ; 3a–c ), , furan-3,4-dicarboxylic acid ( 5 ), furan-3,4-dicarbonyl dichloride ( 6 ), dimethyl 2,5-dibromofuran-3,4-dicarboxylate ( 8 ), selenophene-3,4-dicarboxylic acid ( 12 ), 2,6-bis(trimethyltin)-4,8-di(2-ethylhexyloxyl)benzo[1,2- b :3,4- b ]dithiophene ( 15 ), (4,4′-didodecyl-2,2′-bithiophene-5,5′-diyl)bis(trimethylstannane) ( 16 ), 2,6-dibromo-4,8-di(2-ethylhexyloxyl)benzo[1,2- b :3,4- b ]dithiophene ( 17 ), 5,5′-dibromo-4,4′-didodecyl-2,2′-bithiophene ( 18 ), 5,5″-dibromo-4,4″-didodecyl-2,2′;5′,2″-terthiophene ( 19 ), and 2,6-dibromo-3,5-didodecylbisthieno[3,2- b :2′,3′- d ]thiophene ( 20 ) were prepared according to the literature. Tetrahydrofuran was distilled over sodium/benzophenone system.…”

Furan derivatives of group IV elements (review)

“…Cleavage of the Si-Cfury q bond in 5-trimethylsilyl-2-furoic acid and its ester with bromine+ gave a high yield (more than 80%) both in carbon tetrachloride [307][308][309] and in acetonitrile [308], but demetallation of the ethyl ester [308] by sulfuryl chloride with the formation of the corresponding chlorine derivative (yield 82%) was only observed in acetonitrile. In the same solvent iodination by iodine monochloride took place smoothly at room temperature [308].…”

“…The action of various halogenating agents (sulfuryl chloride, bromine, iodine monochloride) on 5-trimethylsilyl-2-furancarboxylic acid [307], its ethyl ester [308], and 2-trimethylsilyl-3,4-bis(methoxycarbonyl)furans [309] led to electrophilic substitution of the silyl group. Cleavage of the Si-Cfury q bond in 5-trimethylsilyl-2-furoic acid and its ester with bromine+ gave a high yield (more than 80%) both in carbon tetrachloride [307][308][309] and in acetonitrile [308], but demetallation of the ethyl ester [308] by sulfuryl chloride with the formation of the corresponding chlorine derivative (yield 82%) was only observed in acetonitrile.…”

Synthesis of multi-substituted furan rings: the role of silicon

“…Tanaka and co-workers 20 have been investigating how silylated furan rings behave towards conditions that favor ipsosubstitution. Treatment of 35a or 35b (prepared via Diels-Alder chemistry), with sulfuryl chloride, bromine or iodine monochloride afforded 36a-e in yields ranging from 64-76% (Scheme 9).…”