Lactones 1-subst

Cyclopentene derivatives with carboxylic acid side-chains can be stereoselectively hydroxy-lated by the iodolactonization procedure (E.J. Corey, 1969, 1970). To the trisubstituted cyclopentene described on p. 210 a large iodine cation is added stereoselectively to the less hindered /J-side of the 9,10 double bond. Lactone formation occurs on the intermediate iod-onium ion specifically at C-9ar. Later the iodine is reductively removed with tri-n-butyltin hydride. The cyclopentane ring now bears all oxygen and carbon substituents in the right stereochemistry, and the carbon chains can be built starting from the C-8 and C-12 subst> "An,c... 

An efficient conversion of cyclobutanone to a 7-lactone ring is part of a total synthesis of prostaglandins Among the various products obtained by reaction of acetylenes with carbon disulfide are those of special interest which originate by the addition of third components to intermediate 1,3-dithiolium carbenes to form 2-subst. 1,3-dithioles... 

An ethereal soln. of -propiolactone added dropwise at 0° to a stirred soln. of methylenetriphenylphosphorane prepared from methyltriphenylphosphonium bromide and NaNHg in tetrahydrofuran, after 0.5 hr. the resulting betaine (Y 85%) heated at 220° under Nag 7-butyrolactone (Y 74%). F. e., also subst. lactones, s. H. Kise et al., Chem. Commun. 1976, 299. 

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