Phosphine-Catalyzed Diastereoselective Synthesis of β-Lactones from Disubstituted Ketenes and α-Chiral Oxyaldehydes.
In this article we describe a catalytic procedure for the diastereoselective synthesis of β-lactones bearing two stereogenic centers, from disubstituted ketenes and α-chiral oxyaldehydes. Tri-n-butylphosphine was found to be the optimal catalyst in terms of effecting both good yield and diastereoselectivity (dr from 3:1 to 32:1 for 8 examples) in β-lactone formation. The major isomer of the β-lactone products was determined to be the anti-diastereomer, and its formation was rationalized by a polar Felkin-Anh model. Involvement of phosphonium enolate intermediates in the reaction mechanism was indicated through reaction monitoring by (31)P NMR spectroscopy. The utility of the methodology is demonstrated by a short synthesis of a (+)-peloruside A synthon.
†Department of Chemistry, Oakland University, 2200 North Squirrel Road, Rochester, Michigan 48309-4477, United States.
Mukulesh
M
Mondal
†Department of Chemistry, Oakland University, 2200 North Squirrel Road, Rochester, Michigan 48309-4477, United States.
Shi
S
Chen
†Department of Chemistry, Oakland University, 2200 North Squirrel Road, Rochester, Michigan 48309-4477, United States.
Nabil
N
Othman
‡Department of Chemistry, Eastern Illinois University, 600 Lincoln Avenue, Charleston, Illinois 61920-3099, United States.
Kraig A
KA
Wheeler
†Department of Chemistry, Oakland University, 2200 North Squirrel Road, Rochester, Michigan 48309-4477, United States.
Nessan J
NJ
Kerrigan