Synthese neuer, 3-substituierter 2H-Thiopyran-Derivate via [4+2]-Cycloaddition mittels acceptorsubstituierter Enaminothione
摘要:
3- and 4-Nitro acetophenones as well as 3- and 4-trifluoromethyl acetophenones react with POCl3/DMF (Vilsmeier reagent) to give dimethyliminium perchlorates 1a-d after addition of perchloric acid to the reaction mixture. Substitution of the chloro atom in 1 by using sodium sulfide nonahydrate occurs under mild conditions (in case of nitro compounds at -5-degrees-C) leading to enaminothiones 2a-d. Reactions with acroleine and methylvinylketone in refluxing benzene give exclusively 2H-thiopyran derivatives 4a-h, which were isolated in good yields after spontaneous fast elimination of dimethylamine. In contrast, the introduction of 1-nitro-2-phenylethene as the dienophile allows stepwise reaction to give stable adducts 3k and 3l, respectively, and also 3m under mild conditions (reaction at room temperature). H-1 n.m.r. spectroscopic data as well as the elimination of dimethylamine to 4k-m permit the elucidation of the structure of adducts 3k-m.
Pyridinderivate aus 3-Chlor-2-propeniminiumsalzen und Enaminen
作者:Bernd Brinker、Dieter Heber
DOI:10.1002/ardp.19873200608
日期:——
Reaktionen der 3‐Chlor‐2‐propeniminiumsalze 1 führen in Abhängigkeit von der Struktur der Enamine 2, 3 und 21 entweder zu den 1,4‐Dihydropyridinen 8 und 9 oder zu einem Gemisch der isomeren 5‐ bzw. 7‐arylsubstituierten Pyrido[2,3‐d]pyrimidine 22 und 23, deren Struktur anhand der 1H‐NMR‐Spektren diskutiert wird.
The title compounds were synthesized by reaction of nitroketene animals with beta-chlorovinylcarbonyl compounds. The chloromethylene malononitriles 1 react with nitromethylenimidazolin (2 a) and -benzimidazoles 2 b to yield the 8-nitro-2,3-dihydroimidazo[1,2-a]pyridines 3 and the 4-nitropyrido[1,2-a]-benzimidazoles 6, both containing an amino group. Analogously, from the special 3-chloro-2-propeniminium salt 7 and 2 a the imidazopyridine derivative 9 was formed. The 3-aryl-3-chloro-2-propeniminium salts 10 were converted into the nitro-dihydroimidazo[1,2-a]pyridines 11 and the pyrido[1,2-a]benzimidazole 12 containing the aryl group by reaction with 2 a and 2 b, respectively. The structures were investigated by 2-dimensional H-1/C-13-NMR-spectroscopy.
An efficient, regiocontrolled synthesis of 5-aryl-2-carbethoxypyrroles from 3-aryl-3-chloropropeniminium salts
作者:John T. Gupton、Dale A. Krolikowski、Richard H. Yu、Vu Phong、James A. Sikorski、Maria L. Dahl、Claude R. Jones
DOI:10.1021/jo00046a033
日期:1992.9
A variety of 3-aryl-3-chloropropeniminium salts react with alpha-amino acid esters under basic conditions to produce 2-carbethoxy-5-arylpyrroles in a regioselective manner. The overall process represents a short, efficient, and convergent synthesis of 2,5-disubstituted pyrroles, and azomethine ylides or azapentadienyl anions may be involved as intermediates.
SCHNEIDER P.; FISCHER G. W., J. PRAKT. CHEM., 1980, 322, NO 2, 229-236