Reaction of dithiomalonic acid dianilide with substituted acetylenic ketones

The reaction of dithiomalonic acid dianilide with 1-benzoyl(2-thienyl, 2-furoyl)-2-phenylacetylenes in glacial acetic acid in the presence of equimolar amount of perchloric acid under heating (90–115°C) was used to prepare 6-anilino-2-(acylmethyl)-2-phenyl-4-(phenylimino)-4H-1,3-dithiinium perchlorates in good yields.     

Chemo-, regio- and stereospecific addition of adenine and 8-azaadenine to α,β-acetylenic γ-hydroxy nitriles: a short-cut to novel acyclic adenosine analogues

Adenine (9H-purin-6-amine) adds readily to available α,β-acetylenic γ-hydroxy nitriles under mild conditions (molar ratio 1:1, K₂CO₃, DMF, rt, 10 min) to afford chemo-, regio- and stereospecifically (Z)-3-(6-amino-9H-purin-9-yl)-4-hydroxy-4-alkyl-2-alkenenitriles, novel functionalized acyclic nucleoside analogues (95-98% yield). Under similar conditions (K₂CO₃, DMF, rt, 1 h), 8-azaadenine (3H-[1,2,3]triazolo[4,5-d]pyrimidin-7-amine) reacts with 4-hydroxy-4-methyl-2-pentynenitrile nonselectively at the 7-, 8- and 9-positions to give the corresponding adducts in a 1:10.5:9 ratio, the total yield being 81%. Chemo-, regio- and stereospecific addition of 8-azaadenine to the above α,β-acetylenic γ-hydroxy nitriles leading to (Z)-3-(7-amino-2H-[1,2,3]triazolo[4,5-d]pyrimidin-2-yl)-4-hydroxy-4-alkyl-2-alkenenitriles in 44-90% yield is attained when the reaction is carried out without solvent in the presence of Et₃N (30 mol %), the molar ratio of 8-azaadenine:α,β-acetylenic nitriles being 1:2.0 (rt, 12-38 h).     

Synthesis and photochromism of a series of new 2-unsubstituted 3-(2-benzylbenzoyl)quinolin-4(1H)-ones

Synthesis and characterization of a series of new 2-unsubstituted 3-(2-benzylbenzoyl)quinolin-4(1H)-ones is described. In addition to their potential biological activity, these compounds exhibit photoreversible photochromic properties in anaerobic conditions. Using the 1 and 2D NMR techniques we demonstrated that the coloration occurred owing to the formation of fluorescent 5a,6-dihydrobenzo[b]acridin-(5H)-ones. The photoreaction is stereoselective and the S,R-isomers are the major products (83%) whereas the S,S-isomers are the minor (6%). In addition, the irreversible formation of two oxidation products, 3-(2-benzoylbenzoyl)quinolin-4(1H)-ones, and acridin-12(5H)-one derivatives was observed in the presence of air.     

Thiophene-2-carbaldehyde and benzaldehyde thiosemicarbazones in reactions with propargyl bromide and 1,3-dibromopropyne

The reaction of thiophene-2-carbaldehyde and benzaldehyde thiosemicarbazones with propargylbromide in methanol provided S-(2-propyne)thiosemicarbazones hydrobromides of thiophene-2-carbaldehyde and benzaldehyde. Reaction products obtained from thiosemicarbazones and 1,3-dibromopropyne in methanol at heating were 2-thenilydene(benzylidene)azino-4-bromomethylidene-4,5-dihydrothiazol-3-ium bromides.     

Organylthiochloroacetylenes: IV. Reaction with Thiourea

Alkylthiochloroacetylenes react with thiourea in acetone to form S-(alkylthioethynyl)isothiuronium chlorides and N-[1-(alkylthio)ethylidene]thioureas; phenylthiochloroacetylene reacts with thiourea to give 4-(phenylthio)-2-imino-1,3(3H)-thiazole hydrochloride.     

Dynamics of Instabilities in a Viscous Fluid Rotating with an Acceleration

The flow of a viscous incompressible fluid between coaxial cylinders rotating with a constant rigid-body acceleration about the axis is studied numerically. A one-dimensional time-dependent solution of the Navier-Stokes equations is constructed analytically for the motion starting from the state of rest. On the initial time interval the one-dimensional unsteady fluid motion is unstable. Small perturbations introduced into the flow initiate the formation of secondary vortex flows with a velocity component along the axis. The dynamics of the developing instabilities and their dissipation are studied numerically. A condition determining the dimensions of the unsteady secondary flow zone is formulated. The unsteady regime is transient and starting from a certain instant of time the flow becomes stable.