Regioselective synthesis of polysubstituted pyrazoles and isoxazoles.

A regioselective synthesis has been developed for the preparation of unsymmetrical 1,3,5-triaryl-4-alkylpyrazolines and -pyrazoles by treatment of alpha-benzotriazolyl-alpha,beta-unsaturated ketones with monosubstituted hydrazines followed by alkylation at the 4-position of the pyrazoline ring. Reaction of alpha-benzotriazolyl-alpha,beta-unsaturated ketones with hydroxylamine gives 3,5-disubstituted isoxazoles regioselectively.

Regiospecific synthesis of 4-(2-oxoalkyl)pyridines.

[reaction: see text]. A new and operationally simple method has been developed for the regiospecific syntheses of 4-(2-oxoalkyl)pyridines from ketones and pyridine in good yields, using triflic anhydride to activate the pyridine ring.

Conversions by dimethyldioxirane of 1-alkylbenzotriazoles into their N-oxides and of 2-alkylbenzotriazoles into 2-alkyl-trans-4,5,6,7-diepoxy-4,5,6,7-tetrahydrobenzotriazoles.

Dimethyldioxirane converted 1-alkylbenzotriazoles 4 to the corresponding 3-alkylbenzotriazole 1-oxides 5 in good yields, but transformed 2-alkylbenzotriazoles 12 into 2-alkyl-trans-4,5,6,7-diepoxy-4,5,6,7-tetrahydrobenzotriazoles 13.

Dibenzo[b,h][1,4,7]thiadiazonines: examples of a novel ring system.

Acetanilides 1a-e react with 1,1'-sulfinylbis(benzotriazole)/trimethylchlorosilane at 45-65 degrees C to form 1,2-di(benzotriazol-1-yl)-2-arylimino-1-ethanethiones 3a-e, while heating the same reagents at 110 degrees C results in dibenzo[b,h][1,4,7]thiadiazonines 5a,c,d, and 6. X-ray crystal structures are reported for three representative examples.

One-carbon homologation of carboxylic acids via BtCH(2)TMS: a safe alternative to the Arndt--Eistert reaction.

Carboxylic acids are converted into the corresponding homologated acids or esters, using easily available 1-(trimethylsilylmethyl)benzotriazole (1) as a one-carbon synthon. The effectiveness of the reaction has been investigated on six aryl and seven alkyl carboxylic acids.

Novel one-step synthesis of thiazolo[3,2-b]1,2,4-triazoles.

[reaction: see text] Reactions of chalcones 3a-f with bis(1H-1,2,4-triazolyl) sulfoxide 4 formed the thiazolo[3,2-b]1,2,4-triazoles 5a-f, which resemble closely some previously prepared COX-2 inhibitors. The structure of 5a was confirmed by X-ray analysis.

Efficient syntheses of imidazolo[1,2-a]pyridines and -[2, 1-a]isoquinolines.

2-Aminopyridines 1a-c and 1-aminoisoquinoline with 1-chloromethylbenzotriazole give 2-amino-1-[alpha-benzotriazol-1-ylmethyl]pyridinium chlorides 2a-c and 1-amino-2-(alpha-benzotriazol-1-ylmethyl)isoquinolinium++ + chloride 12, respectively. Compounds 2a-c and 12 react with aryl aldehydes 3a-h to afford imidazolo[1,2-a]pyridines 7a-k and imidazolo[2, 1-a]isoquinolines 13a,b in good yields.