Regio- and diastereoselective ene reaction of 4-phenyl-1,2,4- triazoline-3,5-dione with chiral allylic alcohols and their derivatives

Article abstract of DOI:10.1021/jo980835g

Chiral allylic alcohols 1a-e reacted with 4-phenyl-1,2,4-triazoline- 3,5-dione (PTAD) in CH₂Cl₂ to produce 3-amino-1-alken-4-ols 2 and 3 in 78- 89% yields, with 68-90% diastereomeric excess (de) in favor of the threo isomer. Chiral allylic ethers 1f,g and acetates 1h,i gave similar yields but lower de (34-66%). Reaction of allylic alcohols 6a-e with PTAD in CH₂Cl₂ produced 1,3-regioisomers 7 and 8 exclusively in 33-65% yields without apparent diastereoselectivity, except when R₁ was a Bu(t) group, in which case only syn product 7 was formed. However, when 6a or 6c was subjected to reaction with PTAD in a polar solvent, up to 88% de was observed. Reaction of allylic ethers 6f,g and acetates 6h,i with PTAD in CH₂Cl₂ also produced 7 and 8 exclusively with improved yields (56-96%) and diastereoselectivity (50- 100% de in favor of the syn isomer).