The hetero Diels–Alder reaction featuring 2-phenyl-4-dimethylamino-1-thia-3-azabuta-1,3-diene as diene component: a clear example of a thermodynamically-controlled process

Regio- and π-Facial Selective Cycloadditions Involving 2-Phenyl-4-dimethylamino-1-thia-3-azabuta-1,3-diene and Allenic Esters: An Efficient Route to Novel 6-Alkylidene-6H-2-phenyl-5-ethoxycarbonyl-1,3-thiazines

“…It has been reported 24 that the reaction of the heterodiene 4 with dienophiles such as methyl acrylate and methyl methacrylate is reversible and final product distribution is thermodynamically controlled, with more stable trans-or anti-adduct predominating. It has also been reported 24 that no cycloadduct is isolated under toluene-reflux conditions due to retero-cycloaddition at higher temperature. However, in the present case the reactions of diene 4 with allenic esters have been mainly carried out by refluxing in benzene, and in case of adduct derived from allenic ester 5e the major product has anti-stereochemistry involving dimethylamino group at C4 and ethoxycarbonyl moiety at C5.…”

“…The investigations were also of considerable interest because the targeted 1,3-thiazines have drawn considerable interest recently on account of their chemical and pharmaceutical significance. [15][16][17][18][19][20][21][22][23][24] We report herein that thermal cycloadditions of hetero-diene 4 with allenic esters (ethyl 2,3-dienoates, 5), in refluxing CH 2 Cl 2 -benzene, occur regioselectively involving mainly electrondeficient C2-C3 p-bond of allenic esters; the initially formed cycloadducts 6 after elimination of elements of dimethylamine afford novel (E/Z)-6-alkylidene-6H-2phenyl-5-ethoxycarbonyl-1,3-thiazines 7 and 8 in high yields (Scheme 2, Table 1).…”

A chiral 3,4-dihydro-2H-thiopyran compound

“…Asymmetric hetero Diels±Alder reaction appears to be the method of choice for the highly ef®cient regio-and stereoselective synthesis of various heterocycles in enantiomerically pure form (Waldmann, 1994). In the course of an ongoing project (Trippe  et al, 2002) and in view of previous results obtained in our laboratory (Marchand et al, 1995), we isolated the substituted dihydro-2H-thiopyran resulting from the [4+2] cycloaddition reaction of dimethyl (2E)-[(dimethylamino)methylene]-3-thiosuccinate (Tea Gokou et al, 1985) and (4S)-3-acryloyl-4-benzyl-1,3-oxazolidin-2-one (Evans et al, 1984) in the presence of MgBr 2 as catalyst. Only two diastereoisomers, in a 7/3 ratio, were obtained at the end of the reaction and these were separated by chromatography on SiO 2 .…”