Green synthesis of new acyl hydrazide derivatives by single and double aza-Michael reaction under solvent-free conditions

<p>In this paper, we describe a new, simple and efficient strategy for the formation of novel and valuable acyl hydrazide derivatives from reaction between diverse acyl hydrazides and <i>α</i>,<i>β</i>-unsaturated esters in the presence of 1,4-diaza-bicyclo[2,2,2]octane (DABCO) – an inexpensive base – and tetrabutylammonium bromide (TBAB) – an ionic organic salt – under solvent-free conditions. In the reaction, double Michael adducts were produced in good yields in 7 h when acrylic esters were used as Michael acceptors. Surprisingly, no double Michael adducts were produced with fumaric esters, and single Michael adducts were the only products of these reactions in 10 h.</p

Organic-salt-mediated highly regioselective <i>N3</i>-alkylation of 2-thiophenytoin via Michael reaction under solvent-free conditions

<p>A regioselective <i>N3</i>-alkylation of 5,5-diphenyl-2-thiohydantoin (2-thiophenytoin) using a very efficient mild base K₂CO₃ and α,β-unsaturated esters in the presence of organic salt TBAB (tetrabutylammonium bromide) at room temperature has been reported (<b>3b</b>–<b>3h</b>). 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 the <i>N1,N3</i>-dialkylated derivatives of 2-thiophenytoin in good yields (<b>4b</b>–<b>4g</b>). We were unable to selectively <i>N3</i>-alkylate 2-thiophenytoin with ethyl acrylate at both room temperature and 70°C under the same conditions (<b>4a</b>). Dimethyl and diethyl fumarates cannot work as Michael acceptors and were hydrolyzed to fumaric acid under reaction conditions.</p

Green synthesis of novel isatin thioketal derivatives under solvent-free conditions

<p>A new series of spiro[[1,3]dithiolane-2,3′-indolines]-2′-one derivatives was synthesized using Michael addition reaction of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one to various α,β-unsaturated esters as well as direct alkylation of this compound with alkyl dihalides. Michael reaction of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one and α,β-unsaturated esters produced related Michael adduct in the presence of tetrabutylammonium bromide and base 1,4-diazabicyclo[2.2.2]octane in good to excellent yields at 80°C under solvent-free conditions. Also, direct alkylation of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one by dihaloalkanes in the presence of base K₂CO₃ afforded the corresponding products in good yields under the same conditions.</p

Solvent-free organic salt media mono symmetrical aza-Michael: synthesis of new N-mono substituted phthalhydrazide derivatives

<p>In this paper, C–N bond formation between 2,3-dihydrophthalazine-1(4<i>H</i>),4-dione (phthalhydrazide) and <i>α</i>,<i>β</i>-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.</p

A facile synthesis and antibacterial activity of novel pyrrolo[3,4-b]quinolin-2(3H)-yl)benzamides

<p>A new series of pyrrolo[3,4-b]quinolin-2(3H)-yl)benzamides were designed based on molecular hybridization approach and synthesized by reaction of benzohydrazide derivatives with 9-phenylfuro[3,4-b]quinoline-1,3-diones in the presence of an Et₃N catalyst. Simple reaction, excellent yield, simple separation process and eco-friendly approach by minimizing the chemical waste renders this protocol particularly attractive. The series <b>9a–g</b> was evaluated for <i>in vitro</i> antibacterial activity against (+ve bacteria) <i>Staphylococcus aureus</i> ATCC 25923 and <i>Enterococcus faecalis</i> ATCC 29212, (−ve bacterium) <i>Escherichia coli</i> ATCC 25922. <i>In vitro</i> minimum inhibitory concentration (MIC) evaluations showed that the compound <b>9a</b> was effective against <i>E. coli</i> (MIC: 0.25 mg/mL) <i>S. aureus</i> (MIC: 0.25 mg/mL) and <i>E. faecalis</i> (MIC: 0.5 mg/mL).</p