[3+2]-Cycloaddition of 2-(tert-butylsulfanyl)propenoic acid derivatives to cyclooctyne

2001 ARKIVOC  
The title compounds 1a,b being α-acceptor-substituted tert-butyl vinylsulfides add to cyclooctyne; upon warming dioxane solutions of 1a,b for two days 2, 3,4,5,6,7,8,9octahydrocycloocta[b]thiophenes 7a,b were formed in good yield, accompanied by loss of isobutene. Scheme 1 If alkyl groups other than tert-butyl are attached to the sulfur (or selenium) atom, elimination Issue in Honor of Prof. Fritz Sauter ARKIVOC 2001 (ii) 135-138 We wondered whether a cyclic alkyne, being activated by ring
more » ... ivated by ring strain rather than by electron demand, would also undergo the above reaction. Cyclooctyne (5), readily accessible from cyclooctene, 5 was treated with a 40% excess of each of 2-(tert-butylsulfanyl)-propenonitrile (1a) 6 and methyl 2-(tert-butylsulfanyl)propenoate (1b) 7 in dioxane solution at reflux temperature for 60 or 48 h, respectively (Scheme 2). Excess starting materials were separated off chromatographically.
doi:10.3998/ark.5550190.0002.215 fatcat:s72hzmiflnbqhbrd4ytivwg3he