作者:Nancy K. Brennan、David J. Donnelly、Michael R. Detty
DOI:10.1021/jo026635t
日期:2003.4.1
The reaction of N, N-diethyl 4-(N, N-dimethyl-amino)-2-phenylselenobenzamide (7a), N, N-diethyl 4-methoxy-2-phenylselenobenzamide (7b), N, N-diethyl 4-(N, N'-dimethylamino)-2-[(3-(N, N-dimethylamino)phenylseleno]benzamide (7c), and N, N-diethyl 4-methoxy-2-(3-methoxy-phenylseleno)-benzamide (7d) with excess lithium diisopropylamide (LDA) gave 2-N, N-(dimethylamino)-9H-selenoxanthone (9a), 2-methoxy-9H-selenoxanthone (9b), 2,7-bis-N, N-(dimethylamino)-9H-selenoxanthone (9c), and 2,5-dimethoxy-9H-selenoxanthone (9d) in 70%, 59% 23%, and 90% isolated yields, respectively. N, N-Diethyl 2-phenylselenobenzamide (2-Se) gave no reaction with LDA, t-BuLi, MeLi, or lithium 2,2,6,6-tetramethylpiperidide as base. Electron donation from the 4-substituent of benzamide derivatives 7a-7d may increase the directing ability of the carbonyl oxygen to metalate the 2-position of the arylseleno group.