Direct catalytic asymmetric aldol-type reaction of aldehydes with ethyl diazoacetate

The direct aldol-type condensation of aldehydes with ethyl diazoacetate catalyzed by the chiral complex of BINOL derivatives-Zr(O(t)Bu)(4) gave beta-hydroxy alpha-diazo carbonyl compounds with moderate enantioselectivities (53-87% ee). [reaction: see text]     

Development of the enantioselective addition of ethyl diazoacetate to aldehydes: asymmetric synthesis of 1,2-diols

A novel synthetic strategy toward the asymmetric synthesis of vicinal diols bearing a tertiary center is presented. The method encompasses the dinuclear Mg-catalyzed asymmetric addition of ethyl diazoacetate into several aldehydes, oxidation of the diazo functionality, and diastereoselective alkyl transfer of various organometallics into the resulting chiral β-hydroxy-α-ketoesters to afford a diverse range of 1,2-diols in high yield, diastereoselectivity, and chirality transfer.     

Efficient synthesis of 2,6-disubstituted-5-hydroxy-3-oxo-2,3-dihydro-pyridazine-4-carboxylic acid ethyl esters

A general procedure is described for the preparation of 6-substituted-5-hydroxy-3-oxo-2,3-dihydro-pyridazine-4-carboxylic acid ethyl esters (6-substituted-5-hydroxy-3(2H)-pyridazinone-4-carboxylic acid ethyl esters). These compounds are shown to undergo selective alkylation at the 2-position in moderate to good yields (19-77%) to afford 2,6-disubstituted-5-hydroxy-3-oxo-2,3-dihydro-pyridazine-4-carboxylic acid ethyl esters (2,6-disubstituted-5-hydroxy-3(2H)-pyridazinone-4-carboxylic acid ethyl esters).     

Alginic acid hydrazide and its reactions with aromatic aldehydes

Alginic acid hydrazide was prepared, and its reactions with aromatic aldehydes were studied. The effect of a substituent in the benzene ring of the aldehyde on the number of arylidene groups introduced into the polymer was examined.     

Reactions of aromatic aldehydes and their acetals with phosphorous acid esters

Russian Journal of General Chemistry -     

Novel condensations of nitroacetic esters with aromatic aldehydes leading to 5-hydroxy-1,2-oxazin-6-ones

Contrary to the early literature [Dornow, A.; Wiehler, G. Justus Liebigs Ann. Chem. 1952, 578, 113–121], esters of 2,4-dinitro-3-arylglutaric acids 2 could not be obtained by double condensation of aryl aldehydes with alkyl nitroacetates. Instead, under these conditions, we observed formation of novel 4-aryl-5-hydroxy-1,2-oxazin-6-one-3-carboxylates 1. The roles of the solvent, the reaction conditions, and the nature of the reagents in this new condensation were investigated. The data obtained suggest that the heterocyclic products 1 originate from intramolecular oxidation (similar to the Nef reaction) of dinitro derivative 2, followed by nucleophilic attack of the oxime oxygen at the carboxylate group. The condensation presented provides a novel general synthetic route to these types of heterocycle.     

Catalytic aldol-type reaction of aldehydes with ethyl diazoacetate using quarternary ammonium hydroxide as the base

The direct aldol-type condensation of aldehydes with ethyl diazoacetate (EDA) promoted by an organic base and non-metallic catalyst such as tetrabutylammonium hydroxide (TBAOH) gave β-hydroxy-α-diazocarbonyl compounds with moderate to excellent yields. Furthermore, the reactivity and scope of various phase-transfer catalysts as well as electronically divergent aldehydes are discussed.     

Novel tandem reactions of ethyl acetoacetate with aromatic aldehydes: product- and stereo-selective formation of highly functionalised cyclohexanones

The five-component tandem reaction of ethyl acetoacetate with aromatic aldehydes in the presence of pyrrolidine affords t(3),t(5)-diaryl-t(4)-[(E)-3-aryl-2-propenonyl]-r(2)-ethoxycarbonylcyclohexanones stereoselectively in good yields presumably via a tandem Knoevenagel condensation-Michael addition-condensation via enamine-deethoxycarbonylation-Michael addition sequence. The same reactants in the presence of DBU led to the formation of t(3)-aryl-r(2),c(4)-bisethoxycarbonyl-c(5)-hydroxy-t(5)-methylcyclohexanones in excellent yields via a tandem Knoevenagel condensation-Michael addition-aldol reaction sequence.     

Michael reactions of unsubstituted aromatic chiral imines with substituted unsaturated acid esters

The Michael reaction of chiral imines 1–3, derived from aromatic ketones’ with substituted electrophilic olefins generated asymmetric tertiary carbon centers. Nevertheless, asymmetric inductions were weaker than those usually observed with cycloalkanone imines.     

Bisphosphonate prodrugs: synthesis of new aromatic and aliphatic 1-hydroxy-1,1-bisphosphonate partial esters

Methods for the preparation of various 1-hydroxy-1,1-bisphosphonate partial esters were developed. They were obtained from (alkyl or phenyl) bis(trimethylsilyl) phosphite and aromatic or aliphatic acid chlorides, followed by methanolysis.     

Ph3As-catalyzed wittig-type olefination of aldehydes with diazoacetate in the presence of Na2S2O4

In the presence of sodium hydrosulfite and a catalytic amount of AsPh3 and Fe(TCP)Cl, aldehydes react with ethyl diazoacetate to give the corresponding alpha,beta-unsaturated esters in high yields with excellent stereoselectivities (E/Z > 50/1).     

BH3-catalyzed oligomerization of ethyl diazoacetate: the role of C-boron enolates

In contrast to trialkyl boranes, the reaction of borane (BH3) and ethyl diazoacetate (EDA) generates dimer, trimer, and oligomers of EDA. The products arise from double, triple, and multiple insertions of CHCO2Et groups in B-C bonds. On the basis of NMR spectroscopic data, trapping experiments, and computational studies, a novel C-boron enolate has been identified as a key intermediate in this reaction. This C-boron enolate species is calculated to be 7.1 kcal/mol (gas phase) more stable than its isomeric O-boron enolate form. Both spectroscopic data and trapping results also reveal the formation of a doubly borylated enolate generated as a side product by a proton transfer between the C- and O-boron monoenolates.     

Chelate synthesis of 3-ethoxycarbonyl-4-hydroxy-2-trifluoromethylpyridine from ethyl acetoacetate and trifluoroacetonitrile

Ethyl 2-acetyl-3-amino-4,4,4-trifluoro-2-butenoate was synthesized by treatment of ethyl acetoacetate with CF₃CN in the presence of Ni(acac)₂. Condensation of the diphenylboron chelate of the former with dimethylformamide dimethylacetal followed by refluxing in ethanol yielded 3-ethoxycarbonyl-4-hydroxy-2-trifluoromethylpyridine.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1329–1331, July, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08964).     

Chiral phosphinothiourea-catalyzed asymmetric Morita-Baylis-Hillman reactions of acrylates with aromatic aldehydes

A series of chiral bifunctional phosphinothioureas were synthesized and applied to the enantioselective Morita-Baylis-Hillman reaction of aromatic aldehydes with acrylates. In the presence of 8 mol % of organocatalyst 2e, the Baylis-Hillman adducts were obtained in good enantioselectivities and up to 96% yield under mild reaction conditions.