Studies on the Diastereoselective Intramolecular Pauson-Khand Reaction on Regioisomeric Chiral Perhydrobenzoxazines Derived from (-)-8-Aminomenthol

Chiral perhydrobenzoxazines derived from (–)‐8‐aminomenthol and containing a 1,6‐enyne moiety participate in intramolecular diastereoselective Pauson–Khand reactions with diastereoselection that depends on the nature of the starting compounds. 3‐Propargyl‐2‐vinyl‐substituted perhydrobenzoxazines yielded the cyclization products with low diastereoselectivity except for compounds where the double bond was 1,2‐disubstituted. Regioisomeric perhydrobenzoxazines with the acetylenic bond at C‐2 and an allyl substituent at the nitrogen atom gave much better stereochemical discrimination. Chiral perhydrobenzoxazines derived from (–)‐8‐aminomenthol and containing a 1,6‐enyne moiety participate in intramolecular diastereoselective Pauson–Khand reactions leading to cyclization products with moderate to good diastereoselectivity. The diastereoselection depends on both the substitution pattern of the double bond and the regiochemistry of the starting perhydrobenzoxazines