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Enantioselective Formation of Bicyclic Lactones by Rhodium‐Catalyzed Intramolecular CH‐insertion reactions

1994; Wiley; Volume: 77; Issue: 3 Linguagem: Inglês

10.1002/hlca.19940770307

1522-2675

Paul Müller, Philippe Polleux,

Asymmetric Synthesis and Catalysis

Abstract The decomposition of cyclohexyl diazoacetate ( 5a ) in the presence of the chiral [Rh 2 {(2 S )‐mepy} 4 ] catalyst leads to a 3:1 cis/trans mixture of bicyclic lactone 6a with an enantiomeric excess of 95–97% ( cis ) and 90% ( trans ). The conformationally rigid tert ‐butyl derivatives 5b and 5c afford, in the presence of the same catalyst, 6b and 6c , respectively, via insertion into the equatorial CH bonds exclusively, with ee's of ca. 95%. A remarkable degree of induction (92–95%) results in the lactone 6g upon decomposition of 1‐isopropyl‐2‐methylpropyl diazoacetate ( 5g ). The diazoacetates derived from 1‐methylcyclohexanol, cyclopentanol and 1‐methylcyclopentanol ( 5d–f ) afford under similar conditions insertion products with higher diastereoselectivity, but significantly lower enantioselectivity. Other dirhodium catalysts are less efficient.