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Facile Chemo-, Regio-, and Diastereoselective Approach to cis-3,5-Disubstituted γ-Butyrolactones and Fused γ-Butyrolactones

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posted on 02.02.2007, 00:00 by Md. Merajuddin Baag, Vedavati G. Puranik, Narshinha P. Argade
Chemoselective SN2‘ condensation of primary enolates of alkyl methyl ketones 2ae with dimethyl bromomethylfumarate (1) followed by highly diastereoselective NaBH4 reduction of the ketone function in the formed ketodiesters 3ae and the regioselective in situ lactonization of the unisolable intermediates 4ae exclusively furnished the cis-3,5-disubstituted γ-butyrolactones (±)-5ae in very good yields. Similarly, the face-selective coupling reaction of cyclohexanone enolate with 1 to form a mixture of diastereomers in an 8:2 ratio followed by a highly selective reductive cyclization of 9 plus 10 exclusively provided the cis-octahydrobenzofuran (±)-12 in 70% overall yield.