Butyrolactones, reactions with alkyl halide

Bamford-Stevens reaction of the tosylhydrazones of the readily available tetrahydrofuran-3-ones provides a useful synthesis of 2,3-dihydrofurans which may be dehydrogenated to furans with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (66CJC1083). Tetrahydrofuran-2-ones (y-butyrolactones) may be alkylated in the 3-position with LDA and an alkyl halide. The products on reaction with phenyl selenylchloride and LDA, and subsequent oxidation, yield 3-alkylfuran-2(5//)-ones reducible with DIBAL to furans (75JOC542). 

The formation of the endocyclic double bonds of unsaturated lactones has been accomplished via the rDA reaction. The preparation of 2-alkyl-2-butenolactones, such as (179), by a method that incorporates the rDA reaction as a key step has been a q>lied to the synthesis of butyrolactone lignans such as ( >-hinokinin (180) as shown in equation (80). An extensive study of the preparation of substituted 2-bute-nolides (183) has been reported. The mono-, di- and tri-alkyl bicyclobutenolides are prepared by reacting adducts (181) with Grignard reagents or with LDA followed by alkyl halides. Alkylated adducts (182) were then either directly distilled under vacuum or heated in a sealed tube to give the alkylated 2-bute-nolides (183) (equation 81). " ... 

Thus, traMi-3-alkyl-6-(phthalimido)cyclopentenes were prepared in excellent to modest yields from the corresponding tran -chloroalkene by the palladium coupling reaction [84d]. Inexpensive and efficient Pd-TMG systems, Pd(OAc)2-TMG or PdC -TMG, have been developed for the Heck reaction of an olefin with an aryl halide, in which TMG (1) acts as a ligand [84e]. In the reaction of iodobenzene with butyl acrylate the turnover numbers were up to 1000000. TMG (1) was used as a base for the palladium catalysed asymmetric Wagner-Meerwein shift of nonchiral vinylcyclopropane and cyclobutane derivatives leading to asymmetric synthesis of cyclobutanones, cyclopentenones, y-butyrolactones and 5-valerolactones [85] (Scheme 4.34). Replacement of TMG (1) with an inorganic bases such as lithium or cesium carbonate resulted in little effect. 

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