Regio- and stereoselective ring-opening reactions of cyclopropenones: α-methylene-γ-butyrolactones via additions of trichlorocyclopropenylium ions to alkenes

✍ Scribed by Klaus Musigmann; Herbert Mayr; Armin de Meijere

• Publisher: Elsevier Science
• Year: 1990
• Tongue: French
• Weight: 227 KB
• Volume: 31
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)88780-8

✦ Synopsis

The 2-chloro-3-(2'~chloroalkyl)cyclopropenones 4, readily obtained by hydrolysis of the adducts of the m'chlorocyclopropenylium ion onto alkenes, thermally rearrange to propiolic acid chlorides 6. Treatment of 4 with TosOHJ+O in CH,Cl, yields the (E)-3-chloro-2-(2'-chloroalkyl)acrylic acids 9, which have been converted in two simple steps to a-methylene-y-butyrolactones 11 with good overall yields.

Trichlorocyclopropenylium (1) salts usually react with alkenes 2 to give [1:21-and [l:3]-products,2 but in nitromethane solution, the selective formation of the [l:l]-adducts 3 has been accomplished.3 The hydrolysis of l-substituted trichlorocyclopmpenes like 3 has been found to give the chlorocyclopropenones 4.3*4

In this communication we report conditions to selectively cleave the C-l/C-3 bond or the C-l/C-2 bond of 4, and we describe a novel access to a-methylerie-r-butyrolactones 11.