Convenient Synthesis of .ALPHA.-Trifluoromethylated Acyloins from .ALPHA.-Hydroxy or .ALPHA.-Amino Acids.
作者:Masami KAWASE、Setsuo SAITO、Teruo KURIHARA
DOI:10.1248/cpb.48.1338
日期:——
acyloins (2 and 6) have been prepared from alpha-hydroxy acids (1), N-acylprolines (5) or N-acyl-N-alkyl alpha-amino acids (8) by novel transformation reactions with trifluoroacetic anhydride (TFAA) in the presence of pyridine. The former reaction of 1 could proceed through mesoionic 1,3-dioxolium-4-olates, whereas the latter two reactions of alpha-amino acids (5 and 8) could involve mesoionic 1,3-oxazolium-5-olates
Unusual reactions of secondary amino acids with trifluoroacetic anhydride: A novel access to α-trifluoromethylated acyloins
作者:Masami Kawase
DOI:10.1016/0040-4039(94)88187-1
日期:1994.1
A new fragmentation reaction of secondary α-amino acids with trifluoroaceticanhydride under Dakin-West reaction conditions proceeds through oxazolium salt intermediates followed by ring cleavage to form α-trifluoromethylated acyloins in good yields.
The base-catalyzed reaction of N-acylprolines with trifluoroaceticanhydride proceeds through mesoionic 1,3-oxazolium-5-olates followed by the pyrrolidine ring cleavage to afford the 5-trifluoromethyloxazoles in good yields.