Ethanol → (4S,5R)-2,4-Diphenyl-4,5-dihydrooxazole-5-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

Ethanol (0.1 ml) was mixed with tetrahydrofuran (1.0 ml), and the mixture cooled to -78° C. n-Butyllithium (n-BuLi) (2.12M, 0.050 ml) was added dropwise, and the mixture warmed to 0° C. Solid (4S-cis)-4,5-dihydro-2,4-diphenyl-5-oxazolecarboxylic acid, ethyl ester having the structure: ##STR34## (20 mg, 0.0678 mmol) was added and the reaction was stirred for 1 hour (a small amount of water was present). A mixture of cis oxazoline ethyl ester starting material and the corresponding trans oxazoline ethyl ester (5-position inversion) were observed by TLC (very little hydrolysis was noted at this point). The reaction mixture was stirred for another hour and then left with an ice bath overnight (0° C. to room temperature). After 18 hours TLC showed mostly the trans acid title product and a trace of the cis ester starting material (solvent systems hexane:EtOAc 2:1 (trace of cis ester) and EtOAc:acetone:H2O:MeOH 7:1:1:1 (title product)).

Provenance & Evidence