The thiopyran route to polypropionates revisited: Selective syn and anti aldol reactions via 3,6-dihydro-4-trimethylsilyloxy-2H-thiopyran

Article abstract of DOI:10.1016/S0040-4039(97)00337-7

Aldol reaction of the amine free Li enolate of tetrahydro-4H-thiopyran-4-one with 1,4-dioxa-8-thi aspiro[4.5]decane-6-carboxaldehyde gives mainly the 2,3-anti-3,4-syn aldol (7:1) in good yield; reaction of the LDA generated lithium enolate proceeds poorly. Using the trimethylsilyl enol ether and TiCl₄ gives the 2,3-syn-3,4-syn aldol (>10:1). The adducts can be used for polypropionate synthesis.