Highly stereoselective construction of spiro[4.5]decanes by SmI(2)-promoted ketyl radical mediated tandem cyclization
Masaharu Inui1, Atsuo Nakazaki, Susumu Kobayashi
1Faculty of Pharmaceutical Sciences, Tokyo University of Science (RIKADAI), 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Abstract:
[reaction: see text] Ketyl radical mediated tandem cyclization of omega-alkynyl carbonyl compounds bearing activated alkene using SmI(2) gave spiro[4.5]decanes stereoselectively. In the presence of HMPA, alpha,beta-unsaturated esters and alkenyl phosphonates were converted to spiro[4.5]decanes and a monocyclic compound, respectively. In the presence of Sm, bicyclic lactones were obtained from alpha,beta-unsaturated esters. The spiro[4.5]decane was provided from an alkenyl phosphonate. Interestingly, the stereochemical changeover at the first cyclization has been controlled by means of a variety of activators.
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