‘In situ’ Generated ‘HCl’ - An Efficient Catalyst for Solvent-Free Hantzsch Reaction at Room Temperature: Synthesis of New Dihydropyridine Glycoconjugates
Synthesis of 3,4-dihydropyrimidin-2(1H)-ones and 1,4-dihydropyridines using ammonium carbonate in water
作者:Fatemeh Tamaddon、Zahra Razmi、Abbas Ali Jafari
DOI:10.1016/j.tetlet.2009.12.098
日期:2010.2
known and new3,4-dihydropyrimidin-2(1H)-ones and 1,4-dihydropyridines are prepared efficiently via Biginelli and Hantzsch reactionsusing ammonium carbonate in water. Competition between Biginelli and Hantzsch reactions is observed with pyridine carbaldehydes. Using this methodology, Hantzsch esters are synthesized in higher yields and purities than with other procedures without the use of a catalyst
Covalently Anchored Sulfonic Acid on Silica Gel as an Efficient and Reusable Heterogeneous Catalyst for the One-Pot Synthesis of Hantzsch 1,4-Dihydropyridines under Solvent-Free Conditions
A highly efficientone-potsynthesis of Hantzsch 1,4-dihydropyridines under solvent-free conditions catalyzed by sulfonicacid covalently anchored onto the surface of silica gel is reported here. All types of aldehydes, including aromatic, unsaturated, and heterocyclic aldehydes, gave excellent yields. The silica gel/sulfonicacidcatalyst (SiO 2 -SO 3 H) is completely heterogeneous and can be recycled
Reaction of <i>N</i>-Vinylic Phosphazenes with α,β-Unsaturated Aldehydes. Azatriene-Mediated Synthesis of Dihydropyridines and Pyridines Derived from β-Amino Acids
作者:Francisco Palacios、Esther Herrán、Concepción Alonso、Gloria Rubiales、Begoña Lecea、Mirari Ayerbe、Fernando P. Cossío
DOI:10.1021/jo060775b
日期:2006.8.1
Aza-Wittig reaction of N-vinylic phosphazenes (1,2 addition), derivedfrom diphenylmethylphosphine or derivedfrom trimethylphosphine with α,β-unsaturated aldehydes, leads to the formation of 3-azatrienes through a [2 + 2]-cycloaddition−cycloreversion sequence. The presence of an alkyl substituent in position 3 of N-vinylic phosphazenes increases the steric interactions, and [4 + 2] periselectivity
used as substrates to obtain chiral Hantzsch-type 1,4-DHPs, which are frequently contained in pharmaceuticals. The inert C−H bond was converted into a versatile C−Br bond, which enabled the modification of the chiral 1,4-DHP derivatives with high efficiency by nucleophilic substitution. Furthermore, axially chiral 4-aryl pyridines were accessible by central-to-axial chirality conversion.