C5‐disubstituted Meldrum's acid precursors were shown to be a useful platform for the synthesis of an array of 3‐alkylated dihydrocoumarins with up to 93:7 er, thanks to an enantioselective domino cyclization‐decarboxylative‐protonation reaction triggered by an unprecedented benzhydryl‐derived cupreine organocatalyst. This cyclization sequence was extended to an emerging organocatalytic decarboxylative‐chlorination
Multi-catalysis cascade reactions based on the methoxycarbonylketene platform: diversity-oriented synthesis of functionalized non-symmetrical malonates for agrochemicals and pharmaceuticals
作者:Dhevalapally B. Ramachary、Chintalapudi Venkaiah、Y. Vijayendar Reddy、Mamillapalli Kishor
DOI:10.1039/b901652j
日期:——
In this paper we describe new multi-catalysis cascade (MCC) reactions for the one-pot synthesis of highly functionalized non-symmetrical malonates. These metal-free reactions are either five-step (olefination/hydrogenation/alkylation/ketenization/esterification) or six-step (olefination/hydrogenation/alkylation/ketenization/esterification/alkylation), and employ aldehydes/ketones, Meldrum's acid, 1,4-dihydropyridine/o-phenylenediamine, diazomethane, alcohols and active ethylene/acetylenes, and involve iminium-, self-, self-, self- and base-catalysis, respectively. Many of the products have direct application in agricultural and pharmaceutical chemistry.
Synthesis of Mannich Bases of Meldrum's Acid and Its 5-Substituted Derivatives
作者:Jing-Hua Li、Zhen-Chu Chen
DOI:10.1080/00397910008086872
日期:2000.7
Abstract Mannichbases of Meldrum's acid and its 5-substituted derivatives were synthesized using aminomethyl acetate or diaminomethane and acetic anhydride as aminomethylating agent.
Synthesis of functionalized γ-lactams by a lewis acid catalyzed ketene formation/cyclization/claisen rearrangement sequence of 5,5-disubstituted Meldrum’s acid
ketenes using Meldrum’s acid as ketene precursor. Derivatives of Meldrum’s acid with tertiary ammonia structure were used as raw material, and the reaction was catalyzed by Lewis acid at high-temperature conditions under microwave. Ketene formation by losing acetone and CO2, cyclization and claisen rearrangement occurred in sequence to form the γ-lactams.
SYNTHESIS OF ISOPROPYLIDENE 5-ALKYL-5-HYDROXY-METHYLMALONATES AND THEIR APPLICATION TO THE PREPARATION OF 2-ALKYLACRYLIC ACIDS
作者:Zhen-Chu Chen、Jing-Hua Li、Wei-Ke Su
DOI:10.1081/scc-100000531
日期:2001.1
Hydroxymethylated derivatives of isopropylidene 5-alkylmalonates 3 were synthesized, via which 2-alkylacrylic acids 4 were prepared using isopropylidene 5-alkylmalonates 1 as starting materials.