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.
The oxidation of diphenyldiselenide with ammonium peroxydisulphate is a very simple and efficient method to produce phenylselenium cations in the absence of nucleophilic counter ions. The reaction carried out in the presence of an olefin, in acetonitrile or propionitrile containing trifluoromethanesulphonic acid and water afforded the amidoselenenylation products in good yield. The intramolecular
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.