Synthesis of 2-iminothiazoline derivatives by sequential conjugate addition/annulation/ring-opening reactions

Synthesis of dihydrothiophenes or spirocyclic compounds by domino reactions of 1,3-thiazolidinedione

The domino reactions of 1,3-thiazolidinedione, malononitrile, and aromatic aldehydes in the presence of different organic amines were studied. Secondary amines such as pyrrolidine, piperidine, morpholine, and dimethylamine and primary amines such as benzylamine yield dihydrothiophene derivatives through a domino ring-opening/recyclization reaction of 1,3-thiazolidinedione. Bulky diethylamine, diisopropylamine, and 1,4-diazabicyclo[2.2.2]octane give spirocyclohexano-1,3-thiazole through a double Michael addition/spirocyclization reaction.

(Z)-N-[3-(2-Methoxyphenyl)-4-phenyl-2,3-dihydrothiazol-2-ylidene]-2-methylbenzamide

In the title mol­ecule, C₂₄H₂₀N₂O₂S, the thia­zole and amide groups are essentially coplanar. The thia­zole ring forms dihedral angles of 61.62 (4) and 26.75 (5)° with the benzene rings of the methoxy­phenyl and methyl­phenyl groups, respectively, and 33.69 (6)° with the phenyl ring. The crystal packing is stabilized by inter­molecular C—H⋯O hydrogen bonds, forming a three-dimensional network.

(Z)-N-[3-(2-Methoxy-phen-yl)-4-phenyl-2,3-dihydro-thia-zol-2-yl-idene]-4-methyl-benzamide

Geometric parameters of the title compound, C(24)H(20)N(2)O(2)S, are in the usual ranges. The central heterocycle makes dihedral angles of 41.29 (4) and 72.94 (5)° with the phenyl ring and the methoxy-phenyl ring, respectively.