TY - JOUR
T1 - Mechanism of hydrogen atom transfer in the photolytic rearrangement of N-bromophenylalaninamide derivatives
AU - Easton, Christopher J.
AU - Merrett, Martin C.
AU - Razzino, Pasquale
PY - 2000/4
Y1 - 2000/4
N2 - Photolysis of N-bromo-N-tert-butyl-Na-phthaloylphenylalaninamide gave a 1:1 mixture of the diastereomers of 3-bromo-N-tert-butyl-Na-phthaloylphenylalaninamide. Reactions carried out with various concentrations of the N-bromoamide, and in the presence of 4-tert-butyltoluene, showed that the ratio of the product bromophenylalanine derivatives to 4-tert-butylbenzyl bromide varied as a function of the concentration of the N-bromoamide, indicating that the bromophenylalanine derivatives are formed through an intermolecular process and not by intramolecular 1,4-hydrogen atom transfer of the corresponding amidyl radical. Results of reactions of N-bromo-N-tert-butyl-Na-phthaloyl-p-methylphenylalaninamide are also consistent with this interpretation. Reactions of stereoselectively β-deuteriated derivatives of N-bromo-N-tert-butyl-Na-phthaloylphenylalaninamide established that the pro-S benzylic hydrogen of the phenylalaninamide is selectively abstracted, by a factor of ca. 3.8, in this intermolecular process.
AB - Photolysis of N-bromo-N-tert-butyl-Na-phthaloylphenylalaninamide gave a 1:1 mixture of the diastereomers of 3-bromo-N-tert-butyl-Na-phthaloylphenylalaninamide. Reactions carried out with various concentrations of the N-bromoamide, and in the presence of 4-tert-butyltoluene, showed that the ratio of the product bromophenylalanine derivatives to 4-tert-butylbenzyl bromide varied as a function of the concentration of the N-bromoamide, indicating that the bromophenylalanine derivatives are formed through an intermolecular process and not by intramolecular 1,4-hydrogen atom transfer of the corresponding amidyl radical. Results of reactions of N-bromo-N-tert-butyl-Na-phthaloyl-p-methylphenylalaninamide are also consistent with this interpretation. Reactions of stereoselectively β-deuteriated derivatives of N-bromo-N-tert-butyl-Na-phthaloylphenylalaninamide established that the pro-S benzylic hydrogen of the phenylalaninamide is selectively abstracted, by a factor of ca. 3.8, in this intermolecular process.
UR - http://www.scopus.com/inward/record.url?scp=0034175156&partnerID=8YFLogxK
U2 - 10.1039/a908968c
DO - 10.1039/a908968c
M3 - Article
SN - 0300-9580
SP - 693
EP - 697
JO - Journal of the Chemical Society. Perkin Transactions 2
JF - Journal of the Chemical Society. Perkin Transactions 2
IS - 4
ER -