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In this work, a novel series of N and S-alkylated derivatives of 1-phenyl tetrazole-5-thione were synthesized by Michael addition in organic salt media TBAB (Tetrabutylammonium bromide) using inorganic base K2CO3 under solvent-free conditions. The new and conveniently synthesized products showed unusual regioselectivity during the reaction. S-Michael adducts via reaction between 1-phenyl tetrazole-5-thione and acrylic esters as well as acrylonitrile were afforded at room temperature and N-Michael adducts obtained at 70°C. Both reactions occurred within 24 h. Surprisingly, using fumarate esters as Michael acceptor proceeded a SN2 reaction at 100°C due to steric effects. The structures of products all were confirmed by 1H and 13C NMR spectra and target compound yields were good to excellent. [ABSTRACT FROM AUTHOR]

In this paper, C–N bond formation between 2,3-dihydrophthalazine-1(4H),4-dione (phthalhydrazide) andα,β-unsaturated esters was investigated and a new series of phthalazine derivatives was synthesized using an efficient and simple method under solvent-free conditions. An aza-Michael addition of phthalhydrazide to both acrylic and fumaric esters led to N-mono-substituted phthalhydrazides (as mono-Michael adduct) in the presence of tetrabutylammonium bromide as a high polar media, and 1,4-diaza-bicyclo[2,2,2]octane as an available organic base. In this reaction, the N1,N2-bis-Michael adduct was not observed at all. Also, reactions were performed at 90°C and yields of products were good to excellent. [ABSTRACT FROM PUBLISHER]

A regioselectiveN3-alkylation of 5,5-diphenyl-2-thiohydantoin (2-thiophenytoin) using a very efficient mild base K2CO3and α,β-unsaturated esters in the presence of organic salt TBAB (tetrabutylammonium bromide) at room temperature has been reported (3b–3h). The selectivity of this reaction is excellent and products have been produced in good yields under solvent-free conditions. The increase of the reaction temperature to 70°C mostly disappeared this selectivity and afforded only theN1,N3-dialkylated derivatives of 2-thiophenytoin in good yields (4b–4g). We were unable to selectivelyN3-alkylate 2-thiophenytoin with ethyl acrylate at both room temperature and 70°C under the same conditions (4a). Dimethyl and diethyl fumarates cannot work as Michael acceptors and were hydrolyzed to fumaric acid under reaction conditions. [ABSTRACT FROM PUBLISHER]

An unexpected reaction between 4-phenylurazole and fumaric esters which led to the formation of 5-alkylidene derivatives of hydantoin is described in this paper. The reaction takes place in the presence of tetrabutylammonium bromide (TBAB), and 1,4-diaza-bicyclo[2,2,2]octane (DABCO) at 70 °C under solvent-free conditions. [ABSTRACT FROM AUTHOR]

The highly regioselective C-N bond formation between phenytoin and acrylic/fumaric esters was accomplished. Solvent-free media Michael addition of phenytoin to acrylic esters led to the selective synthesis of N3-substituted phenytoins (as mono-Michael adducts) in the presence of tetrabutylammonium bromide (TBAB) and potassium carbonate under ultrasonic irradiation conditions at room temperature. These reactions produced N1,N3-disubstituted phenytoins (as bis-Michael adducts) at 70 °C. Surprisingly, the addition of phenytoin to fumaric esters, instead of acrylic esters, selectively provided only N3-substituted phenytoins at both room temperature and 70 °C under the same conditions. [ABSTRACT FROM AUTHOR]