Heteroaromatic Dithioacetals, Part II: Evidence of a Novel Mechanism for the Exclusive Formation of Unsymmetrical Dithioacetals.

Abstract

The exclusive production of unsymmetrical dithioacetals in the BF₃·Et₂O catalyzed thioacetalization of aldehydes results from novel and unsuspected mechanistic considerations.

Key words

aldehydes - thiols - condensation - Lewis acids - carbonyl complexes

References

• 1 Gauthier JY. Zajac N. Mayhew DL. Hughes GJ. Martins E. Guay D. Young RN. Zamboni RJ. Synlett  1998,  289 ; and references therein
• 3a Young RN. Gauthier JY. Thérien M. Zamboni RJ. Heterocycles  1989,  967 ; and references therein
• 3b Isidor JL. Carson RM. J. Org. Chem.  1973,  554 
• 4 Ravindranathan T. Chavan SP. Tejwani RB. Varghese JP. J. Chem. Soc., Chem. Commun.  1991,  1750 

2

To a 0 °C CH₃CN solution (15 mL) of 2 (2.8 mmol., 0.994 g), 4-chlorobenzaldehyde (2.9 mmol., 0.411 g) and 4-mercaptopyridine (6 mmol., 0.668 g) was added BF₃·OEt₂ (9.7 mmol., 1.2 mL) dropwise. The mixture was allowed to warm to 25 °C and stirred for 16 hours. It was worked up and purified as previously described [1] to yield 1 (1.883 g., 96%).