1. A new approach to 4-alkylthio-1,3-dithiole-2-thione: an unusual reaction of a zinc complex of 1,3-dithole-2-thione-4,5-dithiolate
C Jia, D Zhang, W Xu, D Zhu Org Lett. 2001 Jun 14;3(12):1941-4. doi: 10.1021/ol015990n.
[see reaction]. A new and facile approach to 4-alkylthio-1,3-dithiole-2-thione starting from easily accessible reactants was described. This approach was based on the unusual reaction of a zinc complex of 1,3-dithiole-2-thione-4,5-dithiolate with electrophilic reagents in the presence of 3-picolyl chloride hydrochloride/or 4-picolyl chloride hydrochloride/or pyridine hydrochloride.
2. Efficient enantioselective hetero-Diels-Alder reaction of Brassard's diene with aliphatic aldehydes: a one-step synthesis of (R)-(+)-kavain and (S)-(+)-dihydrokavain
Lili Lin, Zhenling Chen, Xu Yang, Xiaohua Liu, Xiaoming Feng Org Lett. 2008 Mar 20;10(6):1311-4. doi: 10.1021/ol8002282. Epub 2008 Feb 28.
An efficient catalytic asymmetric hetero-Diels-Alder reaction of Brassard's diene with aliphatic aldehydes was reported. The catalyst, which was generated from (R)-BINOL, Ti(i-PrO)4, and 4-picolyl chloride hydrochloride, promoted the reaction smoothly to afford the corresponding alpha,beta-unsaturated delta-lactone derivatives in moderate-to-good yields (46-79%) with high enantioselectivities (up to 88% ee). Natural products (R)-(+)-kavain (70% ee, >99% ee after single recrystallization) and (S)-(+)-dihydrokavain (84% ee) were also prepared in one step by using this methodology.
