5-Alkoxy-butyrolactones

In a similar fashion, 5-alkoxy-butyrolactones can undergo addition and elimination to give substituted 3-pyrrolin-2-ones. In 1973, Farina and coworkers found that 5-methoxyfuran-2-one 575 treated with aqueous ammonia gives 5-hydroxy-3-pyrrolin-2-one 576 (Scheme 165 1973S167). Ten years later. Farina and coworkers showed that primary amines, such as benzylamine, give 5-hydroxy-3-pyrrolin-2-ones when stirred with 2-chloro-5-methoxyfuran-2-one (1983H(20)1761). The transformation... 

Allenyl ethers are useful key building blocks for the synthesis of a-methylene-y-butyrolactones [129, 130], The synthesis of the antileukemic botryodiplodin was accomplished with the crucial steps briefly presented in Scheme 8.56. Bromoallenyl ethers 225 were easily prepared by base-induced isomerization from the corresponding /3-bromoalkyl alkynyl ether compounds and then subjected to electrophilic bro-mination with NBS. The resulting acetals 226 were converted into 2-alkoxy-3-methy-lenetetrahydrofurans 227 by dehydrohalogenation of the alkenyl bromide unit to an alkyne and subsequent radical cyclization employing tributyltin hydride [130],... 

Miscellaneoas Reactions.—Little interest has been shown this year in the photochemistry of alkyl nitrites. Irradiation of the acetylenic nitrite (230) 1 to the formation in poor yield of y-butyrolactone (231). A mechanism involving cyclization of the alkoxy-radical, followed by formation of the spiro-intermediate (232), is shown in Scheme 18. The intramolecular addition of thiiyl radical to... 

Moderate erythro- ecx y Xy is observed in the reaction of the lithium enolate of butyrolactone with ben2aldehyde in the presence of ZnClg. The 3-alkoxy-enolates (157) are methylated to give /roni-butyrolactones (158) in good yield and with approximately 9 1 selectivity (Scheme 92). ... 

---