Tetrahedron p. 623 - 632 (1974)
Update date:2022-08-05
Topics:
Anghelide
Draghici
Raileanu
New dienamino esters (3b-k) were obtained by addition of enamino esters (1b-g) to methyl and ethyl propiolate (2a-b). Z,E-Configuration and a transoid conformation were assigned on the basis of spectral data which indicate also noncoplanarity of phenyl groups whenever present. The corresponding adducts with acetylenedicarboxylic ester (18 and 19) have a cisoid conformation and it was possible to differentiate between thermodynamically and kinetically controlled products. Deuteration experiments showed the existence of a 1,5-proton transfer while comparative examination of a whole series of NMR spectra furnished evidence for a head to tail attachment. Attempts to trap the intermediate zwitterion 10 resulted in the formation of 15a-b corresponding to a cyclobutene intermediate. The reaction repiesents a new synthesis of the benzene nucleus and a practical method to obtain the methyltrimesic and 2,4,6-biphenyltricarboxylic acids. Additions of enamino esters to the triple bond are best interpreted as occurring through a common key intermediate, a zwitterion of type 5 or 10. The former collapses by proton transfer and the resulting imino-derivative 6 tautomerizes to 3. The latter cyclizes to a non-isolable cyclo-butene 12 which by opening of the ring produces the dipolar species 13 which further reacts with propiolic ester. By cyclization of the dienamino esters 3a-j but not of 18 and 19 in dipolar aprotic solvents at 160-190° the corresponding a-pyridones 4a-t were obtained in good yields.
View Morewebsite:http://www.hanwayschem.com
Contact:+86-18502787239(whatsapp)
Address:18-1-802, Green Garden, Jianghan District, Wuhan 430023, China
Jinan Hongfangde Pharmatech Co.LTD
Contact:0531-88870908
Address:F Bldg,750#,Shunhua Rd,New&High-tech Zone,Jinan,Shandong,China 250101
Tianjin Ingenochem Technology Co.,Ltd
Contact:+86-22-23677060
Address:Hitech Green Industry Park K2-9-602, Nankai district
Shanghai Collins & Paulson Pharmaceuticals Co., Ltd.
Contact:15201714675
Address:Room A647-18, Building No. 2, 351 Guoshoujing Road, Shanghai Free Trade Zone
Huaian Double Win Chemicals Co.,Ltd.
Contact:+86-13511538872
Address:Blk 43,Greenland Century Town,Huaian District, Huaian City,Jiangsu Province,China
Doi:10.1039/P19740001970
(1974)Doi:10.1021/jm00198a024
(1979)Doi:10.1002/ardp.19753080211
(1975)Doi:10.1055/s-1975-23737
(1975)Doi:10.1021/jm00242a015
(1975)Doi:10.1021/ja01548a047
(1958)