An unusual rearrangement of the thujane skeleton under free-radical conditions: Synthesis of thioacetates and thiols derivatives of (-)-sabinene

Abstract

Photochemical acetylthiolation of (À)-sabinene 1 afforded 10-acetylthiothujane 2 and an unexpected cyclopentenyl methyl thioacetate 3 in moderate yield (24%). Hydride reduction of these two latter compounds gave two monoterpenoid thiols (2a and 3a) in excellent yield (95%). The odour of the major sulfur-containing compounds 2 and 2a was respectively described as being typically anisic and as reminiscent of cooked leek. Structural determination of these derivatives was achieved by one-and two-dimensional NMR spectroscopy.

Monoterpene Thiols: Synthesis and Modifications for Obtaining Biologically Active Substances

“…The obtained thiols were isolated by preparative capillary GC. Photochemical addition of thioacetic acid to (−)-sabinene 24 gives a mixture of anti Markovnikov bicyclic thioacetate 25 and unsaturated thioacetate 26 in an overall yield o 24% and a 3:1 ratio, respectively [49]. The unexpected formation of thioacetate 26 result from cyclopropane ring cleavage.…”

“…The yield of a by-product, thioacetate 20, from this procedure does not exceed 25%. The best method to obtain Markovnikov product 22 (82%) with a preserving camphane structure was catalysis via In(OTf Photochemical addition of thioacetic acid to (−)-sabinene 24 gives a mixture of anti-Markovnikov bicyclic thioacetate 25 and unsaturated thioacetate 26 in an overall yield of 24% and a 3:1 ratio, respectively [49]. The unexpected formation of thioacetate 26 results from cyclopropane ring cleavage.…”