2005

Cycloaddition reactionsO 0070 Asymmetric 1,3-Dipolar Cycloadditions of 2-Diazocyclohexane-1,3-diones and

Alkyl Diazopyruvates. — The 1,3-dipolar cycloaddition of title diazocyclohexane-diones, e.g. (IV), and diazopyruvates, e.g. (XI), to cyclic and acyclic enol ethers is stud-ied in the presence of various chiral ruthenium catalysts. In general, better results are achieved with the diazopyruvates (up to 74% e.e.) while a phenyliodonium ylide related to diazocyclohexanedione (IV) gives inferior results (below 17% e.e.). The reaction mechanism is discussed and different intermediates are proposed for the reactions of diazodiketones, diazopyruvates and iodonium ylide. — (MUELLER, P.; CHAPPELLET, S.; Helv. Chim. Acta 88 (2005) 5, 1010-1021; Dep. Org. Chem., Univ. Geneva, CH-1211 Geneva 4, Switz.; Eng.) — Mischke

40- 043

2005