Carbon-Carbon Bond Cleavage of .ALPHA.-Hydroxybenzylheteroarenes Catalyzed by Cyanide Ion: Retro-Benzoin Condensation Affords Ketones and Heteroarenes and Benzyl Migration Affords Benzylheteroarenes and Arenecarbaldehydes.
作者:Yumiko SUZUKI、Yuki TAKEMURA、Ken-ichi IWAMOTO、Takeo HIGASHINO、AKira MIYASHITA
DOI:10.1248/cpb.46.199
日期:——
4-(α-Benzyl-α-hydroxybenzyl)quinazoline (4a) underwent retro-benzoin condensation catalyzed by cyanide ion to give deoxybenzoin (2a) and quinazoline (5a). Similarly, several nitrogen-containing heteroarenes (4, 9, 12, 16-19) having an α-hydroxybenzyl group at the α-position of the nitrogen underwent retro-benzoin type condensation to afford ketones (2) and heteroarenes (5). However, similar reaction of pyrazolopyrimidines (13, 14, 15) having an α-benzyl-α-hydroxybenzyl group resulted in benzyl migration, giving benzylpyrazolopyrimidines (8) and arenecarbaldehydes (3). Tetrabutylammonium cyanide (11, Bu4NCN) was a more effective cyanide ion donor than KCN (10). The retro-benzoin condensation was applied to the synthesis of 2-substituted quinazolines (38) from 2-chloro-4-aroylquinazolines (34), using the aroyl group as a protecting and electron-withdrawing group.
4-(α-苄基-α-羟基苄基)喹唑啉(4a)在氰离子催化下经历逆苯偶姻缩合反应,生成脱氧苯偶姻(2a)和喹唑啉(5a)。同样,多个含氮杂环芳烃(4, 9, 12, 16-19)在其氮原子的α位上具有α-羟基苄基的结构,也经历逆苯偶姻型缩合反应,生成了酮(2)和杂环芳烃(5)。然而,具有α-苄基-α-羟基苄基结构的吡唑嘧啶(13, 14, 15)在类似的反应中引发了苄基迁移,生成了苄基吡唑嘧啶(8)和芳烃羰醛(3)。四丁基铵氰(11, Bu4NCN)比KCN(10)更有效地作为氰离子的供体。逆苯偶姻缩合反应被应用于从2-氯-4-芳酰基喹唑啉(34)合成2-取代喹唑啉(38),使用芳酰基作为保护和电子 withdrawing 基团。