Elimination reactions of terminal .beta.-oxy selenoxides. Synthesis of aryl and vinyl enol ethers and of furans, oxazoles, and thiazoles
摘要:
Elimination reactions of terminal selenoxides holding an alkoxy group in the beta position, RCH-(OR)CH2SeOPh, are usually difficult and can give rise to complex reaction mixtures. We report that these reactions take place more easily whenever the oxygen atom is linked to an unsaturated group (-CH=CHR, -Ar, -CR=O, -CH=NR). These selenoxides are easily available, and the elimination reaction was employed to effect useful syntheses of both open-chain and cyclic aryl and vinyl enol ethers. Moreover, by simple isomerization with acids or bases the cyclic derivatives can be transformed into the corresponding furans. The same procedure has been employed to synthesize substituted oxazoles and thiazoles also.
A time-economical and robust synthesis of various selenofunctionalized heterocycles was accomplished via I2O5-mediated selenocyclizations of olefins with diselenides. Using this method, 116 selenomethyl-substituted heterocycles were synthesized with up to 97% isolated yield in minutes. Additional features of this new protocol include the use of an inorganic oxidant, mild conditions, and easy operation
通过I 2 O 5介导的烯烃与二硒化物的硒环化,实现了各种硒官能化杂环的经济且稳健的合成。使用这种方法,在几分钟内合成了 116 个硒甲基取代的杂环,分离产率高达 97%。这个新协议的其他特点包括使用无机氧化剂、温和的条件和易于操作。初步研究表明,这种转化是通过硒基碘诱导的亲电环化进行的。