l-Proline catalyzed asymmetric transfer aldol reaction between diacetone alcohol and aldehydes

Abstract

We demonstrate for the first time, L-proline as a chiral catalyst for transfer aldol reaction between aldehydes and diacetone alcohol.

Solvent free Lewis acid catalyzed vinylogous condensation

“…13 Direct condensation in the presence of a Lewis acid or base has also been observed over the years. 5 But in this context, the results were appreciable only in the presence of a highly acidic methyl or methylene group which will initiate the condensation reaction via carbanion formation. 5 Organic reactions under solvent-free 14 conditions have also increasingly attracted chemist's interest particularly from the viewpoint of green chemistry.…”

“…3 More vividly, among vinylogous reactions, the aldol addition reaction has attracted considerable interest over the years as a popular tool for the construction of new carbon-carbon bonds. 4,5,6 In this class of reactions, the best studied reaction involves the addition of silyl enol ethers to carbonyl compounds in the presence of Lewis bases 7 and Lewis acids 8 as catalyst (Mukaiyama aldol condensation). 4,9 A few other aldol condensations catalyzed by Brönsted bases as well as Lewis acids, to form a metal enolate in situ have also been reported recently in the literature.…”

“…10 Several attempts have resulted in the successful enhancement of the yields of the reaction by changing reaction conditions (such as aqueous medium). 5,11 An active methyl or methylene group on aldehydes appears to be an essential precursor for these reactions to proceed. 12,13 In this, the initial step is the formation of a carbanion, by the action of a base.…”

Peg 400

“…Till date reactions involving PEG 400 have been carried out and investigated, for example, Heck reaction, 2 Lindlar catalytic hydrogenation, 3 asymmetric dihydroxylation, 4 Baylis-Hillman reaction, 5 Biginelli reaction, 6 SuzukiMiyaura coupling, 7 Stille cross-coupling, 8 Wacker reaction, 9 asymmetric aldol reaction, 10 3,4-dihydropyrimidones via Biginelli reaction, 11 Strecker reaction, 12 etc. ..…”

Hypervalent Iodine(III) Sulfonate Mediated Synthesis of 6‐Arylimidazo[2,1‐b]thiazoles in Liquid PEG‐400

“…Furthermore, the cost of ionic liquids is often more expensive than that of PEG. 13 To date some of the more important reactions have been carried out and investigated in PEG, for example, Heck reaction, 14 Lindlar catalytic hydrogenation, 15 asymmetric dihydroxylation, 16 BaylisHillman reaction, 17 Biginelli reaction, 18 Suzuki-Miyaura reaction, Stille cross-coupling reaction, 19 Wacker reaction, 20 and asymmetric aldol reaction, 21 etc.…”