Multicomponent reactions of 1,3-disubstituted 5-pyrazolones and formaldehyde in environmentally benign solvent systems and their variations with more fundamental substrates

Glycerol and derived solvents: new sustainable reaction media for organic synthesis

“…50 Using the aminopolysaccharide 27 as a surfactant-combined basic catalyst, chemoselective ring-opening of epoxides with carboxylic acids to afford the corresponding esters 28 could be achieved in glycerol (Scheme 20). 51 Remarkably, the use of conventional basic catalysts, such as ZnO, K 2 CO 3 or secondary amines, resulted in lower reaction rates and selectivities since formation of ethers, derived from the ring-opening of the epoxides with glycerol, as by-products was observed.…”

“…50 In the first step a 1,3-disubstituted 5-pyrazolone 24 is selectively formed by condensation between phenylhydrazine and the b-keto ester. Subsequent addition of the styrene derivative and paraformaldehyde to the reaction mixture generates 25 through a tandem Knoevenagel/hetero-Diels-Alder reaction.…”

Present Status of Green Solvents

“…물, 톨루엔, 니 트로메탄 또는 무 용매 조건 하에서는 선택성이 결여 되어 소량의 제품만이 생성되고, 부산물이 생기지만, 반응을 글리세롤 내에서 진행시키면 반응 선택성이 극적으로 향상되어 제품을 68%의 수율로 얻을 수 있 다 [44] . [44] HUST의 J. N. Tan 등은 2010년에 단일반응기 내에 서 arylhydrazines, β-ketone esters, formaldehyde 및 스 티렌 등이 관여하는 2단계 탠덤반응에 글리세롤을 용 매로 사용하는 방법과 indoles, arylhydrazine, β-ketone esters 및 para-formaldehdye가 관여하는 반응도 소개하 였다 [45] . [46] .…”

Bleaching earth clay (pH 12.5)/PEG-400: an efficient recyclable catalytic system for synthesis of 5,6,7,8-tetrahydroquinoline-3-carbonitrile derivatives

“…To achieve such tasks, multicomponent reactions (MCRs) have recently emerged as a powerful tool in organic synthesis that allows quick access to the diversity-based library of small organic molecules for medicinal or pharmaceutical chemistry. Due to their valued features such as convergence, productivity, facile execution, and generally high product yield [1][2][3], MCRs have occupied a top position in modern synthetic organic chemistry [1,2]. On the other hand, development of new MCRs with an environmentally benign concept has attracted particular attention because of the possibility that such reactions may comply with the green chemistry protocol [3].…”

“…These include reaction of a,b-unsaturated ketones and anilines with malononitrile under microwave irradiation [23], in the presence of various Lewis acid catalysts such as Sc(OTf) 3 [24] or alkalis such as KOH and Na metal [25][26][27], and metalbased and organocatalysts [28][29][30]; these reactions have also been reported under catalyst-free condition in water [31]. In spite of this, several reported methods suffer from one or more drawbacks, such as using nongreen catalytic systems, toxic reagents, expensive ligands, incomplete conversion of starting materials, long reaction times, and tedious workup procedures with unsatisfactory yields.…”