Stannous chloride-mediated reductive cyclization-rearrangement of nitroarenyl ketones |
| |
Authors: | Bates Dallas K Li Kexue |
| |
Institution: | Department of Chemistry, Michigan Technological University, Houghton, Michigan 49931,USA. dbates@mtu.edu |
| |
Abstract: | Cyclization products are produced in excellent yields from using standard reaction conditions for nitroarene reduction to aminoarene with SnCl2. Thus, 4-methyl-2-(2-nitrobenzyl)-2H-1,4-benzothiazin-3(4H)-one (2b) upon treatment with SnCl2 in ethanol did not produce the expected aniline derivative. Instead, 6-methyl-11a, 12-dihydro-6H-quino3,2-b]1,4]benzothiazine (3) was produced in excellent yield, presumably via novel Sn (IV)-mediated amidine formation from the initial aniline reduction product. Under identical reaction conditions, 2-(2-nitrophenyl)-thiochroman-4-one (6) produces ethyl 5,11-dihydrodibenzob,e]1,4]thiazepin-11-ylacetate (7). A novel semipinacol rearrangement is proposed to account for this extensive skeletal rearrangement. Aniline derivative (14) (from 6 treated with FeSO4.7H2O) forms 12-ethoxy-11,12-dihydro-6H-6,12-methanodibenzob,f]1,5]thiazocine (15) upon treatment with SnCl2 in ethanol. Thiophene analogues of 6 and 14 (18 and 19, respectively) react similarly, forming the analogous thiazepine (20) and cyclic N,O-acetals (21), respectively. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|