Microwave-assisted dealkoxycarbonylation of α-mono- and α,α-disubstituted β-keto- and α-cyanoesters mediated by a silica gel bed

Abstract

An alternative microwave-assisted Krapcho-type reaction of α-mono- and α,α-disubstituted β-keto- and α-cyanoesters was efficiently performed on a silica gel bed.

Synthesis of 1-Azaspiro[4.4]nonane Derivatives Enabled by Domino Radical Bicyclization Involving Formation and Capture of Alkoxyaminyl Radicals

“…The carbomethoxy group (−CO 2 Me) of the esters 16a–c was removed by dealkoxycarbonylation using the Krapcho reaction. 13 Whereas the β-ketoesters 16d–j reacted under a novel modification 14 to the aforementioned reaction affording ketones 17d–j (Table 1). Finally, the ester 16k was dealkoxycarbonylated using the Curran method 15 and lithium chloride (entry 11, Table 1).…”

“…Then, the product was isolated using a gradient of ethyl ether or ethyl acetate or dichloromethane/hexane mixture. 14…”

Synthesis and reactivity of succinylthioimidazolium salts: A unified strategy for the preparation of thioethers

“…[293] This can be challenging in cases of complex target molecules, as one building block has to be a free thiol 225. was found that Carbimazole 230, the prodrug for Thiamazole (an antithyroid agent to treat hyperthyroidism [294] ), did not give the envisaged cationic sulfide intermediate In line with this observation, heating induced and silica gel-mediated dealkoxycarbonylation reactions of α-monosubstituted β-keto-and α-cyanoesters, have been recently reported by the group of M. Jaramillo-Gómez. [295] Since the unexpected reactivity of imidazole-2-thione 230 gave access to 231, the generality of this methodology was tested with further arenes and heteroarenes as nucleophiles.…”

“…28 -7.36 (m, 3H), 7.73 -7.78 (m, 1H) ppm. 13 Dove et al [295] The solution of 1-methyl-1H-benzimidazole-2-thiol (492 mg, 3.00 mmol, 1.00 equiv.) in dry THF (5 mL) was cooled to 0 °C.…”

“…1 H NMR (300 MHz, CDCl3) δ = 1.53 (t, J = 7.1 Hz, 3H) ), 3.76 (s, 3H), 4.60 (q, J = 7.1 Hz, 2H), 7.10 -7.18 (m, 1H), 7.27 -7.37 (m, 2H), 7.83 -7.90, (m, 1H) ppm. 13 Compound 252 was synthesized in modified protocol of S. Dove et al [295] The solution of compound 258 (531.7 mg, 3.00 mmol, 1.00 equiv.) in dry THF (5 mL) was cooled to 0 °C.…”