A highly diastereoisoface-selective intramolecular hetero Diels-Alder reaction of homochiral camphor-derived thiabutadienes to afford novel, optically active bornene ring-fused dihydrothiopyrans is described for the first time.Thiocarbonyl compounds have recently received considerable attention as synthetic tools with specific properties. 1 In fact, such useful sulfur compounds have been proved as key intermediates with rich, specific reactivity in the synthesis of complex molecules and natural products. 2 On the other hand, there are numerous examples of camphor derivatives that have been exploited, particularly as chiral sources. 3 The attractive advantages of employing camphor in asymmetric synthesis are its relatively inexpensive and easy availability, potent transformation ability, and promising asymmetric induction due to the topological differentiation efficiency apparently by virtue of the rigid framework of its derivatives. Salama et al. recently reported the photolysis of thiocamphor for the synthesis of the 3,6-dihydro-1,2dithiin system. 4 Corre et al. have recently demonstrated that thiocamphor derivatives can also be utilized as useful synthons for chiral ligands. 5 Some recent reports also describe the synthesis of homochiral camphor-annulated (fused) heterocycles such as pyridines, 6 pyrroles, 7 pyrazoles, 8 and oxazolines, 9 particularly for the use of chiral ligands. To the best of our knowledge, however, there have been no reports so far of the synthesis of bornene-fused homochiral dihydrothiopyrans. In the course of our investigation on α,β-unsaturated thiocarbonyl compounds, we have reported asymmetric hetero Diels-Alder (HDA) reactions of thiabutadienes to afford optically active dihydrothiopyrans. 10 We considered it worthwhile to incorporate the camphor framework into a heterodiene system for preparing a new chiral thiabutadiene. Furthermore, to the best of our knowledge, there have been no reports on the intramolecular, asymmetric thiabutadiene-Diels-Alder reaction. 11,12 Here, we wish to report for the first time the synthesis of optically active, bornene-fused dihydrothiopyrans that involves a highly diastereoisoface-selective intramolecular HDA cycloaddition of 3-(arylmethylene)thiocamphors bearing a dienophile (2).

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