The Reaction of Patchoulol with Lead Tetraacetate,a Regiospecific Fragmentation

Patchoulol (1) forms 2,2,6,8-tetramethylbicyclo [5.3.1]undec-7-en-3-one (5) with lead tetraacetate. This ketone undergoes acid-catalyzed cyclization to 2,6,6,10-tetramethyltricyclo [5.3.1.0^1,5]undec-9-en-5-ol (10) , and is reduced to 2 stereoisomeric alcohols with lithium aluminium hydride. One of these alcohols 8 is readily dehydrated with cyclization to 2,6,6,10-tetramethyltricyclo [5.3.1.0^1,5]undec-9-ene (12) and a double bond isomer 13 , longer treatment with acid resulting in a Wagner-Meerwein rearrangement to a mixture of two 1,3,7,7-tetramethyltricyclo [6.2.1.0^2,6]-undecenes ( 19 and 20 ), isomeric with β-patchoulene ( 23 ). The other alcohol 7 with p-toluenesulfonic acid forms the cyclic ether, 1,3,7,7-tetramethyl-11-oxatricyclo-[4.4.1.1^2,8]dodecane ( 15 ).