The tert- amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives

• Dipak Prajapati and
• Kalyan Jyoti Borah

Beilstein J. Org. Chem. 2007, 3, No. 43, doi:10.1186/1860-5397-3-43

• effect, which generalizes cyclization of certain derivatives of 3-methyl-1-phenyl-2-pyrazolin-5-ones. Using this strategy a variety of fused heterocycles is obtained by the Knoevenagel condensation of 5-tert-amino-3-methyl-1-phenylpyrazolone-4-carboxal-dehyde 3 with active methylene compounds such as

• Knoevenagel condensation reactions with malonodinitrile to give the corresponding pyrazolin-5-ylmethylenemalonodinitriles 4a, which in turn cyclized in the presence of anhydrous zinc chloride to get the corresponding pyrazolinoquinolizines 6a and 1,4-oxazinopyrazolines 6e in refluxing toluene (Scheme 1). The

• conditions. Similarly, when cyanoacetamide was reacted in place of malonodinitrile and the Knoevenagel product 4b thus obtained was further heated in the presence of zinc chloride, the corresponding pyrazolinoquinolizine 6a was obtained in 60% yield. The structures of the end products obtained were

An improved synthesis of 1,3,5-triaryl- 2-pyrazolines in acetic acid aqueous solution under ultrasound irradiation

• Ji-Tai Li,
• Xiao-Hui Zhang and
• Zhi-Ping Lin

Beilstein J. Org. Chem. 2007, 3, No. 13, doi:10.1186/1860-5397-3-13

• ] Among various pyrazoline derivatives, 2-pyrazolines seem to be the most frequently studied pyrazoline type compounds. A variety of methods have been reported for the preparation of this class of compounds. After the pioneering work of Fischer and Knoevenagel in the 19th century, the reaction of α,β

An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via indium- catalyzed multi- component domino reaction

• Dipak Prajapati and
• Mukut Gohain

Beilstein J. Org. Chem. 2006, 2, No. 11, doi:10.1186/1860-5397-2-11

• Knoevenagel/hetero-Diels-Alder reaction of 1,3-dimethyl barbituric acid with an aromatic aldehyde and ethyl vinyl ether/2,3-dihydrofuran in presence of 1 mol% of indium(III) chloride. The reaction also proceeds in aqueous media without using any catalyst, but the yield is comparatively less (65–70

• reaction of α,β-ethylenic ketones and ethyl vinyl ether or 2,3-dihydrofuran has remained unexplored.[11] Herein, we report the first example of indium(III) chloride catalysed synthesis of fused pyrimidine derivatives via a multicomponent domino Knoevenagel hetero Diels-Alder reaction. The reaction proceeds

• respectively for diastereomer A. The configuration of diastereomer A may therefore be assigned as trans and cis for the diasteromer B. The formation of these heterocycles 5 can be rationalized by initial formation of a conjugated electron-deficient heterodiene by standard Knoevenagel condensation of the