In continuation of our studies on thio Michael addition to levoglucosenone1 we have discovered that secondary thiols connected to aliphatic and aromatic (including heterocyclic) rings form Michael adducts as single stereoisomers. In order to test the reactivity of various exo-cyclic enones prepared from dihydrolevoglucosenone2 in the reactions with thiols as active Michael addition we performed the addition reaction with mercaptoacetaldehyde3 as shown below in the presence of a base catalyst such as triethylamine. The Michael adduct at C-7 reacts to form interesting enantioenriched spiro-tetrahydrothiophene derivatives. The crystalline products were isolated in good (60-65%) yield and characterized by 1H and 13C NMR analysis. A plausible reaction mechanism is discussed. The product compounds were investigated for their antifungal and other biological activities.

Synthesis of enantioenriched spiro-tetradihydrothiophenes via base catalyzed Michael/aldol cascade addition of mercaptoacetaldehyde to exo-cyclic enones

ACS Spring 2022

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