Veneta Dryanska

Photophysical properties and quantum chemical calculations of differently substituted 2(2-phenylethenyl)-benzoxazoles and benzothiazoles

The low fluorescence quantum yield of 2(2-phenylethenyl)-benzoxazoles and benzothiazoles in solution at room temperature is attributed to intramolecular librations with great amplitude of the two heavy fragments at the both ends of the allyl chain. Freezing the solutions at 77 K leads to remarkable increase of fluorescence quantum yield up to three orders of magnitude. No phosphorescence at 77 K is observed. The analysis of the results from quantum-chemical calculations (AM1 approximation) supports the hypothesis for the quenching processes in excited sate.

Phase-Transfer Catalyzed Additions. VII. Preparation of 3-Aryl-3-arylamino-2-(N-diphenylmethyleneamino)-propanenitriles

Abstract The phase-transfer catalyzed reaction of N-diphenylmethyleneaminoace tonitrile 1 with arylidene-anilines 2 gives the title compounds in good yields.

Phase-Transfer Catalyzed Additions. VI. Reaction of N-Diphenylmethyleneaminoacetonitrile with Aromatic Aldehydes

Abstract The phase-transfer catalyzed reaction of N-diphenylmethyleneaminoacetonitrile with aromatic aldehydes affords 4-aryl-3-cyano-1,1-diphenyl-2-aza-1,3-butadienes (3) in good yields.

An Efficient One-Pot Synthesis of 3-(2-Benzothiazolyl)coumarins

Abstract Some 3-(2-benzothiazolyl)coumarin imines and 3-(2-benzothiazolyl)coumarins are prepared from 2-benzothiazolylacetonitrile and 2-hydroxybenzaldehydes in ethanol in the presence of catalytic amount of NaOH.

Phase-Transfer Catalyzed Additions. IV1. Addition of tert-Butyl Phenylacetate to Activated Double Bond

Abstract Tert-butyl phenylacetate is reacted with derivatives of cinnamic acid, chalkone and benzylideneaniline under phase-transfer catalysis conditions to give in good yields the corresponding addition products.

UNCATALYZED KNOEVENAGEL CONDENSATION OF 2-CYANOMETHYLBENZOTHIAZOLE WITH AROMATIC ALDEHYDES. PREPARATION OF 3-ARYL-2-(2-BENZOTHIAZOLYL)-ACRYLONITRILES AND 3-(2-BENZOTHIAZOLYL)-COUMARIN IMINES

Abstract A series of 3-aryl-2-(2-benzothiazolyl)-acrylonitriles (3a-n) and 3-(2-benzothiazolyl)-coumarin imines (5a-f) are prepared in good to high yields by refluxing solutions of 2-cyanomethylbenbenzothiazole (1) and aromatic aldehydes (2, 4) in ethanol.

Phase-Transfer Catalyzed Additions. V1. Addition of N-Diphenylmethylenebenzylamine to α,βUnsaturated Ketones

Abstract Derivatives of 4-amino-1,3,4-triaryl-1-butanone are prepared by addition of N-diphenylmethylene-benzylamine to chalkones under PTC conditions.

NMR spectra and stereochemistry of some 2,3,4,5-tetrasubstituted pyrrolidines

Abstract The relative configurations of diastereomeric 3-benzoyl-4-aryl-2,5-diphenylpyrrolidines have been determined by means of 1 H and 13 C NMR spectroscopy. The results led to conclusions concerning the stereochemistry and the probable mechanism of the reaction used for the synthesis.

A Convenient Synthesis of Esters of β-Phenylglutamic Acid Under Aqueous Conditions

Abstract Several esters of β-phenylglutamic acid (3, 4) are prepared by Michael reaction of glycine ester Schiff bases 1 and 2 under aqueous conditions.

A convenient synthesis of threo-4-amino-3, 4-diphenylbutanoic acid and its derivatives

Several alkyl threo-4-[(diphenylmethylene)amino]-3,4-diphenylbutanoates (3) were prepared by phase-transfer catalysed reaction of N-(diphenylmethylene)benzylamine and esters of cinnamic acid; acid hydrolysis of 3 affords threo-4-amino-3,4-diphenylbutanoic acid.