Asymmetric Synthesis of Thiadecalins via an Organocatalytic Triple Cascade/Sulfa-Michael Sequence

An efficient two-step asymmetric synthesis of highly substituted cis-configured thiadecalins and the corresponding hexahydrobenzothiophene core is described. Thiadecalin derivatives are known for their widespread biological activities, such as antimicrobial and neurotropic properties. The procedure is based on an organocatalytic triple cascade reaction followed by an intramolecular sulfa-Michael addition. In this manner six consecutive stereocentres are controlled and the target molecules are obtained in moderate yields, with virtually complete enantioselectivitiy (ee >99%) and after recystallisation in diastereomeric ratios of>97:3. The relative and absolute configuration was determined by NMR spectroscopy and X-ray structure analysis.