Base-catalyzed endo-mode cyclization of allenes: easy preparation of five- to nine-membered oxacycles.
A reliable and efficient procedure for constructing five- to eight-membered oxacycles has been developed. Allenes with both a phosphoryl group and a suitable delta-hydroxyalkyl side chain at the C1-position underwent an endo mode ring-closing reaction to give five- to seven-membered oxacycles. Changing the phosphoryl group to a phosphono functionality facilitated the preparation of eight-membered congeners. Introduction of a cis double bond to the alkyl side chain of the starting allenes made possible the easy formation of medium-sized oxacycles, such as the dihydrooxocin and tetrahydrooxonin frameworks, regardless of the electron-withdrawing group (POPh2, PO(OEt)2, SOPh, and SO2Ph) at the C1-position.
Mukai
Chisato
C
Division of Pharmaceutical Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan. cmukai@kenroku.kanazawa-u.ac.jp
Ohta
Masaru
M
Yamashita
Haruhisa
H
Kitagaki
Shinji
S