Current Organocatalysis (v.1, #2)

Pyrrolidine Catalyzed Direct Synthesis of 3,5-Diarylcyclohexenones from Acetone and Chalcones by Sandip J. Wagh, Raghunath Chowdhury, Sunil K. Ghosh (71-78).
The organo-catalyzed reaction of chalcones with acetone has been described. Pyrrolidine has been found tocatalyse the cascade Michael-aldol-dehydration of chalcones and acetone to produce 3,5-diaryl cyclohexenones undermild conditions with good yields. The organocatalytic methodology tolerated a range of substituents on both the aromaticrings of chalcones. The cyclohexenones produced are known to be the precursors for 3,5-diarylphenols, 3,5-diarylanilinesand complex heterocycles.

Nine metal-organic frameworks, [M(PDA), M(BTC), M(PTC)] (M=Cu, Co, Mn; H2PDA= pyridine-2,6-dicarboxylic, H3BTC= 1,3,5-benzenetricarboxylic acid , H3PTC= pyridine-2,4,6-tricarboxylate), containing respectivelyCu2+, Co2+, Mn2+ ions and carboxylate ligands (H2PDA, H3BTC, H3PTC). They can be used as valuable heterogeneouscatalysts since they are easily separated and reused from the reaction systems, and possess single catalytic active sites intheir frameworks which are characteristic of the homogenous catalysts. In addition, N-hydroxyphthalimide (NHPI) hasbeen also revealed to be valuable organocatalyst for free-radical processes and found ample applications in promoting theaerobic oxidation of a wide range of organic compounds. We present here a heterogeneous protocol by adsorbing NHPI inMOFs to obtain the novel NHPI/MOFs catalytic system. The allylic oxidation of α-isophorone (α-IP) into ketoisophorone(KIP) utilizing the NHPI/MOFs as heterogeneous catalysts with moleular oxygen as primary terminal oxidant under solvent-free condition was conducted. The results show that NHPI/Co(BTC) obtain optimum catalytic efficiency affording36.6% conservation of ?-IP and 81.7% KIP selectivity. The catalyst can be isolated easily from the reaction system bysimple filtration and recycle without significant degradation in activity. The oxidations fulfill the requirement of greenchemistry concept in terms of environmental benignity and sustainability.

Organocatalysed Cyanations of Carbonyl Compounds by Dina Murtinho, Maria Elisa da Silva Serra (87-106).
One of the most important carbon-carbon bond forming reactions in organic synthesis is the cyanation of carbonylcompounds. The resulting cyanohydrins are key building blocks for many other important compounds, namely, α-hydroxy acids, α-hydroxy ketones, primary and secondary β-hydroxy amines, α-hydroxy esters and α-amino acids, whichare essential in areas such as fine chemistry, agrochemicals and pharmaceuticals. Cyanohydrin synthesis can be catalyzedby enzymes, metal complexes, inorganic and organic componds. The initial synthetic methods have been extensively exploredhowever the organocatalyzed reaction has been referred to in more limited extent. In this paper we will review thecyanation of aldehydes and ketones in the presence of organocatalysts, addressing both the formation of racemic and nonracemiccyanohydrins.

Enantioselective Desymmetrizations Promoted by Bifunctional Organocatalysts by Arianna Quintavalla, Lucia Cerisoli, Elisa Montroni (107-171).
The enantioselective desymmetrization is regarded as an effective strategy for producing chiral compoundsfrom achiral substrates. The past decade saw the establishment of organocatalysis in organic synthesis and also organocatalyticdesymmetrizations have emerged in recent years. In particular, bifunctional organocatalysts have shown the abilityto promote enantioselective desymmetrizations enabling simultaneous covalent and/or non-covalent activations of thereagents. Many classes of prochiral and meso compounds were efficiently desymmetrized, being cyclic anhydrides ringopeningand diols acylation the most widely employed transformations. The goal of this review is to give a comprehensiveoverview on the developed strategies in the field of the enantioselective desymmetrizations promoted by bifunctional organocatalysts.