Malonate radical cyclisations of methylenecyclopropane derivatives

✍ Scribed by Christine Destabel; Jeremy D Kilburn; John Knight

• Publisher: Elsevier Science
• Year: 1994
• Tongue: French
• Weight: 968 KB
• Volume: 50
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)89430-8

✦ Synopsis

Absbuct -Cyclisations of various methyleaecyclqupyl suhstitmed makeate radicals have ken studied. Radicals dexived from makmama 4 and 9 nadavean exclusive S-exe cyclisaticn cab the methylerbxyclcpmpane Anne, followed by cpeaiag of the resulting cycloprq~ylmethyl mdicat, to 8ive methylenecyclohexane products. Radicalsderivedfrcmmalea&a 5 and 10 largely gave kkycb[l.S.O]octanc products, in good yields, as a result of 'I-en& cyclisation. Cyclisation of the radical dexived fmn malonak 11 gave a bicycb[lS.O]nonane derivative in 3 1% yield, as a result of an (I-en& cyclisation. In the preceding paper' we have described studies on the radical cyclisation of methylenecyclopropane derivatives in which we found that (methylenecyclopropyl)pmpyl radicals 1 (n = 1) cleanly gave methylenecyclohexanes resulting from an initial kro cyclisation, and subsequent opening of the intemmd&e cycloproplymethyl radical (Scheme 1). Cyclisation of (methylenecyclopropyl)butyl radicals 1 (n = 2), however, gave a mixture of products resulting from initial -exe and -end0 cyclisation and from straightforward reduction. Cyclisation of (methylenecyclopropyl)pentyl radicals 1 (n = 3) simply gave the reduced, uncyclised product. 1 SCHEME 1 We thetefote decii to look at the cyclisatkm of the corresponding methylenecyclopropyl derived rnalonate mdicals using the atom transfer methodology which has been considembly developed by Curran in recent years.2 This should allow relatively slow cyclisations to pmceed without the reduction observed for methylenecyclopropylbutyl radicals and methyleoecyclopsopylpa~tyl radicals when using tributyltin hydride methodology. In this paper we describe the results of these studies. Using the methodology aheady described,*~ methylenecyclopropane was converted into alcohols 2,3 and 6 -8, by deprotonation. alkylation and subequent removal of the THP protecting group. The alcohols