97549-05-8Relevant academic research and scientific papers
Diastereoselectivity in the Diels-Alder Reactions of Thioaldehydes
Vedejs, E.,Stults, J. S.,Wilde, R. G.
, p. 5452 - 5460 (2007/10/02)
The Diels-Alder reaction of thioaldehydes with cyclopentadiene occurs with a preference for the endo isomer.The highest selectivity is observed for thioaldehydes RCHS where R is a bulky group such as tert-butyl or isopropyl.Thioaldehydes having α-alkoxy, acetoxy, or siloxy substituents also react with useful endo selectivity.Secondary orbital overlap is a small factor in these reactions since α-oxo thioaldehydes react with relatively low endo selectivity.Steric effects are primarily responsible for the endo preferences observed.The Diels-Alder reactions of chiral α-oxygen substituted thioaldehydes also occur with useful thioformyl face selectivity.A Cornforth transition state 5 is most likely for the selectivity observed for α-alkoxy or acetoxy thioaldehydes, but the α-hydroxy analogue 23 reacts with the opposite facial preference.The highest face selectivity is obtained with the acetonide of thioglyceraldehyde, generated by photolysis of the phenacyl sulfide 15b.
