PHOTOCHEMICAL-REARRANGEMENT OF ALPHA-CHLORO-PROPIOPHENONES TO ALPHA-ARYLPROPANOIC ACIDS - STUDIES ON CHIRALITY TRANSFER AND SYNTHESIS OF (S)-(-IBUPROFEN AND (S)-(+)-KETOPROFEN())
Hr. Sonawane et al., PHOTOCHEMICAL-REARRANGEMENT OF ALPHA-CHLORO-PROPIOPHENONES TO ALPHA-ARYLPROPANOIC ACIDS - STUDIES ON CHIRALITY TRANSFER AND SYNTHESIS OF (S)-(-IBUPROFEN AND (S)-(+)-KETOPROFEN()), Tetrahedron, 50(4), 1994, pp. 1243-1260
A new single-step efficient photochemical approach for alpha-arylpropa
noic acids (4) from alpha-chloro-propiophenones (5) is described. It i
nvolves carbonyl triplet exicted state directed 1,2-aryl migration of
the aryl substituent. The mode of this rearrangement is probed by the
study of the photobehaviour of a set of optically active alpha-chloro-
propiophenones. The results suggest that the nature of the carbonyl tr
iplets (pi,pi()/pi,pi(*)) plays an important role in the chirality tr
ansfer. This method finds application in the synthesis of optically ac
tive ibuprogen (4e) and ketoprofen (26), through in moderate optical y
ields.