Novel Formation and Crystal Structure of 2-(2,2,2-Trifluoroethylidene)-6-trifluoro-methyl-2,3-dihydro-4H-1,4-oxazin-3-ones from N-Acetyl-N-alkyl-a-amino Acids
摘要:
The title compounds (2a-g) were formed from N-acetyl-N-alkyl-alpha-amino acids (la-g) on treatment with trifluoroacetic anhydride in the presence of pyridine. The structure of the product (2a) was determined by single crystal X-Ray analysis.
Diphosphine ligands bearing highly symmetric, bulky substituents at a stereogenic P atom were prepared, exploiting established protocols, which include the use of chiral synthons such as 3,4-dimethyl-2,5-diphenyl-1,3,2-oxazaphospholidine-2-borane (3a) and phenylmethylchlorophosphine borane (10) and the enantioselective deprotonation of dimethylarylphosphine boranes. However, only (Bu(t)())(Me)PCH(2)CH(2)P(Bu(t)Me