Synthesis and transformations of (±)‐ trans ‐4aβ( H ), saα(H)‐octahydro‐4α,7β‐dimethyl‐2 H ‐1‐benzopyran‐2‐one

Hydrogenation of 4,7‐dimethylcoumarin ( 1 ) in alkaline medium has been shown to furnish a mixture of (±)‐ trans ‐4aβ( H ),8aα( H )‐octahydro‐4α,7β‐dimethyl‐2 H ‐1‐benzopyran‐2‐one ( 2 ), (±)‐ trans ‐4aβ( H ),8aα( H )‐octahydro‐4α,7α‐dimethyl‐2 H ‐1‐benzopyran‐2‐one ( 3 ) and (±)‐ cis ‐4aα( H ),8aα( H )‐octahydro‐4α,7α‐dimethyl‐2 H ‐1‐benzopyran‐2‐one ( 4 ) in 40:25:35:ratio, respectively. The stereochemistry of the major hydrogenation product 2 , has been established by transforming it to p ‐menthane derivatives e.g . (±)‐2 ( R )‐[2′( R )hydroxy‐4′( R ) methylcyclohex‐(1′ S )‐yl]propan‐1‐ol ( 20 ) and (±)‐ trans ‐3α,6β‐dimethyl‐3aβ( H ),7aα( H )‐octahydrobenzofuran ( 12 ). Starting from a mixture of lactones 2, 3 and 4 , lactone 3 has been obtained in pure state employing a sequence of reactions.