Journal of the Chemical Society. Perkin Transactions 2 (2001) p. 1367 - 1376 (1996)
Update date:2022-09-26
Topics:
Glover, Stephen A.
Jones, Katherine M.
McNee, Ian R.
Rowbottom, Colleen A.
N-Acyl-3,4-dihydro-1H-2,1-benzoxazines (3) undergo a thermal decomposition involving loss of formaldehyde in a retro-Diels-Alder reaction. The resultant N-acylazaxylylenes? (4) undergo a 6π electrocyclisation to give 2-substituted-4H-3,1-benzoxazines (5) rather than a 4π electrocyclisation to give the N-acyl-1,2-dihydrobenzazetes (6). Compounds 5 have been fully characterised spectroscopically and their data is inconsistent with that reported previously by other workers for what are purported to be the same compounds. 2-Methyl-4H-3,1-benzoxazine (5b) and other 2-alkyl-substituted compounds undergo facile hydrolysis to o-aminobenzyl esters (9) which rearrange to the thermodynamically more stable o-hydroxymethylanilides (10). 2-Phenyl-4H-3,1-benzoxazine (5a) is relatively stable to hydrolysis but undergoes a novel photochemical ring opening (> 254 nm) to give the N-benzoylazaxylylene (12) which can be trapped with alcohols giving o′-alkoxymethylbenzanilides (11). In cyclohexanol at 160°C, the intermediate in the thermal rearrangement of 3a to 5a, N-benzoylazaxylylene (12), was trapped as o′-cyclohexyloxymethylbenzanilide (11b). The rearrangements in mesitylene are unimolecular with activation energies of 35, 37 and 42 kcal mol-1 ? for 3a; 3c and 3d, respectively. The extrusion and electrocyclisation reaction pathways for N-acetyl-3,4-dihydro-2,1- benzoxazine (3b) have been modelled using AM1 molecular orbital theory which predicts both a non-synchronous transition state for the retro-Diels-Alder reaction and the preferred mode of ring closure to be the 6π rather than the 4π electrocyclisation.
View MoreJiaozuo Zhongwen Trading Coporation Limited
Contact:+86 0391-3553810
Address:East Renmin Road
Hebei Kangtai Pharmaceutical Co.,Ltd
Contact:+86-0317-3512963
Address:Wugang Road,Mengcun of Cangzhou City,Hebei Province ,China
website:http://www.antaibio.com
Contact:86-21-60939051,60939771
Address:Room 2108, Building 2,No. 489 Zhengli Road,200433
Contact:+86-025-52406782
Address:8 Taizishan Rd., Yanjiang Industrial Development Area, Nanjing, Jiangsu, China.
Contact:86-21-57725962
Address:shanghai
Doi:10.1021/ol900200k
(2009)Doi:10.1021/acs.joc.5b00011
(2015)Doi:10.1055/s-1987-28119
(1987)Doi:10.1002/anie.201914637
(2020)Doi:10.3987/COM-08-11603
(2009)Doi:10.1016/0304-5102(90)85034-F
(1990)