Highly Stereoselective Radical Carbonylations of gem-Dihalocyclopropane Derivatives with CO
摘要:
A couple of radical carbonylations of gem-dihalocyclopropanes 1 using CO and Bu3SnH (formylation) or Bu3Sn(CH2CHCH2) (allylacylation) successfully proceeded to give trans and cis adducts (2 and 3) with good to excellent stereoselectivity (trans/cis = > 99/1-75/25 or 17/83-1/99). The formylation of 2,3-cis-disubstituted 1,1-dihalocyclopropanes enhanced trans selectivity (trans/cis = > 99/1-95/5), whereas both 2,3-cis-disubstituted and 2-monosubstituted 1,1-dihalocyclopropanes underwent allylacylation with nearly complete trans selectivity (trans/cis = > 99/1). Inherently less reactive gem-dichloro- and bromochlorocyclopropanes than gem-dibromocyclopropanes served as favorable substrates.
Sequential and highly stereoselective intermolecular radical additions of 2,3-cis-disubstituted 1,1-dibromo- and 1-bromocyclopropanes to electron-deficient olefins
作者:Yoo Tanabe、Ken-ichi Wakimura、Yoshinori Nishii
DOI:10.1016/0040-4039(96)00156-6
日期:1996.3
Novel and sequential intermolecular radicaladditions of 2,3-cis-disubstituted 1,1-dibromo- and 1-bromocyclopropanes to electron-deficient olefins proceeded with high stereoselectivity, i.e., in an exo-face addition manner. This highly stereoselectiveaddition was also applied to an intramolecular cyclization.