Stannous chloride-mediated reductive cyclization - Rearrangement of nitroarenyl ketones
Document Type
Article
Publication Date
11-29-2002
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-quino[3,2-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-dihydrodibenzo[b,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-methanodibenzo[b,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.
Publication Title
Journal of Organic Chemistry
Recommended Citation
Bates, D.,
&
Li, K.
(2002).
Stannous chloride-mediated reductive cyclization - Rearrangement of nitroarenyl ketones.
Journal of Organic Chemistry,
67(24), 8662-8665.
http://doi.org/10.1021/jo0259921
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/8073