Syntheses and biological activities of 6-aryl-3-(3-hydroxypropyl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazines.

A series of 6-aryl-3-(3-hydroxypropyl)-7H-1,2,4-triazolo[3,4-b][1,3,4]-thiadiazines were synthesized by the reaction of 4-amino-3-(3-hydroxypropyl)-5-mercapto-1,2,4-triazole (1) with substituted omega-haloacetophenones. Their structures were confirmed by elemental analysis, IR, 1H-NMR, and 13C-NMR. Tests of plant growth regulating effects showed that the title compounds display remarkable inhibitory activities on the growth of radish and wheat.

Modification of (1R,2S)-1,2-diphenyl-2-aminoethanol for the highly enantioselective, asymmetric alkylation of N-diphenylphosphinoyl arylimines with dialkylzinc.

Experimental studies on the modification of (1R,2S)-1,2-diphenyl-2-aminoethanol, which is used to promote the alkylation of N-diphenylphosphinoyl benzalimine with diethylzinc, revealed that N-monosubstituted amino alcohols exhibited higher enantioselectivities than their N,N-disubstituted counterparts and imino alcohols. Application of the optimal chiral ligand 3c to activate the reaction of N-diphenylphosphinoyl arylimines with diethylzinc and dibutylzinc resulted in excellent enantiomeric selectivities of up to 98% ee. The origin of the experimentally observed enantioselectivities was revealed by density functional calculations (B3LYP/6-31G*) on the transition structures of several model reactions.

Evaluation of chiral oxazolines for the highly enantioselective diethylzinc addition to N-(diphenylphosphinoyl) imines.

On the basis of the principle that the incorporation of the structurally rigid and conformationally restricted skeleton in beta-amino alcohols is beneficial to the enantioselective diethylzinc addition to imines, a series of chiral oxazolines, which had been designed and conveniently prepared from commercially available (1S,2S)-2-amino-1-phenylpropane-1,3-diol, were applied in the diethylzinc addition to diphenylphosphinoyl imines to give high yields of 68-84% and excellent ee values of 90-95%. The configuration of the product was controlled by the chirality of the carbon bonded to the hydroxyl group in the oxazoline. Oxazolines bearing a para- or meta-substituted phenyl group generally offered higher enantioselectivity than those containing an ortho-substituted phenyl. The X-ray structures of 4f and 4j, in combination with the proposed transition state, preliminarily explained why oxazolines with a para- or meta-substituent on the phenyl group gave higher enantioselectivities than those bearing an ortho-substituent. This successful example using chiral oxazolines to promote the titled reaction implies that a large family of chiral compounds containing an oxazoline ring moiety have the potential to be developed for promoting the highly enantioselective dialkylzinc addition to N-(diphenylphosphinoyl) imines.

Highly enantioselective diethylzinc addition to imines employing readily available N-monosubstituted amino alcohols.

An easily accessible chiral ligand 3c, which promoted diethylzinc addition to imines with 96-98% ee, has been found by finely screening N,N-disubstituted and N-monosubstituted amino alcohols. N-monosubstituted amino alcohols, on average, gave slightly higher enantioselectivities than their N,N-disubstituted analogues. These results imply that the restricted and rigid structure of amino alcohol is not the absolute requirement for the highly enantioselective dialkylzinc addition to diphenylphosphinoylimines. [structure: see text]