Condensation Of Aliphatic Aldehydes Research Articles

Synthesis of 3,4-Dihydropyrimidin-2(1H)-one-phosphonates by the Microwave-Assisted Biginelli Reaction

The synthesis of novel 3,4-dihydropyrimidin-2(1H)-one-phosphonates was elaborated by the microwave (MW)-assisted three-component Biginelli reaction of β-ketophosphonates, aromatic or aliphatic aldehydes and urea derivatives. The condensation was optimized on a selected model reaction in respect of the reaction parameters, such as the heating method, the type of the catalyst and solvent, the temperature, the reaction time and the molar ratio of the starting materials. The fast and solvent-free MW-assisted procedure was then extended for the preparation of further new 3,4-dihydropyrimidin-2(1H)-one-phosphonate derivatives starting from different aromatic aldehydes, β-ketophosphonates and urea derivatives to prove the wide scope of the process. As a novel by-product of the Biginelli-type synthesis of 3,4-dihydropyrimidin-2(1H)-one-phosphonates, the 5-diethoxyphosphoryl-4-phenyl-6-styryl-3,4-dihydropyrimidin-2(1H)-one was also isolated and characterized. Our MW-assisted method made also possible the condensation of aliphatic aldehydes, diethyl (2-oxopropyl)phosphonate and urea, which reaction was previously reported to be impossible in the literature.

Enzymatic Cross‐Benzoin‐Type Condensation of Aliphatic Aldehydes: Enantioselective Synthesis of 1‐Alkyl‐1‐hydroxypropan‐2‐ones and 1‐Alkyl‐1‐hydroxybutan‐2‐ones

AbstractBenzoin‐type reactions have been intensively exploited as a synthetic strategy for the preparation of α‐hydroxy ketones. Thiamine diphosphate (ThDP) dependent enzymes are excellent catalysts for asymmetric versions of such reaction types. In particular, in cross‐benzoin condensations of aromatic reactants and mixed aromatic/aliphatic reactions, use of these enzymes has resulted in high levels of chemo‐, regio‐ and stereoselectivity. The present work, which confirms this trend for aliphatic reactants, outlines results obtained in the formal cross‐benzoin‐type condensation of the ‘umpoled’ acetaldehyde and propionaldehyde with various aliphatic aldehydes catalyzed by the ThDP‐dependent enzyme acetoin:dichlorophenolindophenol oxidoreductase (Ao:DCPIP OR). In these reactions, 3‐hydroxy‐3‐methylbutan‐2‐one (methylacetoin) was used as the activated acetaldehyde donor, while 4‐hydroxy‐4‐methylhexan‐3‐one was employed for the first time as the precursor of activated propionaldehyde. With the exception of 3‐hydroxypentan‐2‐one and 3‐hydroxyhexan‐2‐one, which were obtained in almost racemic form by the condensation of methylacetoin with propanal and butanal, respectively, all other products achieved from reactions performed using the same donor with more hindered aldehyde acceptors were obtained with high conversions (89–99%) and in good to high enantiomeric excess (72–99% ee). In a similar way, high conversions (75–99%) and good ee (76–99%) were observed in reactions performed with the same set of aldehyde acceptors, but using 4‐hydroxy‐4‐methylhexan‐3‐one as propionyl anion donor. This is the first time that most of the products described herein have been prepared via benzoin‐type condensation.magnified image

Synthesis of functionalized alkyl-substituted cyclohexanones, pyridines, and 2,3,5,6,7,8-hexahydroisoquinolines by condensation of aliphatic aldehydes with CH acids

Functionalized alkyl-substituted cyclohexanones, pyridines, and 2,3,5,6,7,8-hexahydroisoquinolines were synthesized by condensation of aliphatic aldehydes with CH acids.

ChemInform Abstract: A Stereoselective Route to Polysubstituted Tetrahydroquinolines by Benzotriazole-Promoted Condensation of Aliphatic Aldehydes and Aromatic Amines.

By the promotion of benzotriazole (20 mol %), two molecules of anilines (or other arylamines) and two molecules of phenylacetaldehyde (or o-bromophenylacetaldehyde) condensed to give a series of 1,2,3,4-tetrahydroquinolines in a stereoselective manner. By the catalysis of SmI(2) or SmI(3), the N-(alpha-aminoalkyl)benzotriazoles derived from anilines and (R)-glyceraldehyde acetonide dissociated to the corresponding iminium and enamine species, which underwent asymmetric [4 + 2] cycloadditions to give optically active tetrahydroquinolines.

Synthesis of Substituted Cyclobutane and Aniline Derivatives by Condensation of Aliphatic Aldehydes with Malonodinitrile

Synthesis of Substituted Cyclobutane and Aniline Derivatives by Condensation of Aliphatic Aldehydes with Malonodinitrile

Synthesis of 4-alkyl-6-amino-3,5-dicyano-2(1H)-pyridinethiones

Condensation of aliphatic aldehydes with cyanothioacetamide has given 4-alkyl-6-amino-3,5-dicyano-2(1H)-pyridinethiones, which have also been synthesized by recyclization of 4-alkyl-2,6-diamino-4H-thiopyrans. Substituted 2-alkylthiopyridines and thieno[2,3-b]pyridines have been prepared from the pyridinethiones. 2,6-Diamino-4-isopropyl-3,5-dicyano-4H-thiopyran and 6-amino-4-isobutyl-2-methylthio-3,5-dicyanopyridine have been studied by x-ray crystallography.

The use of aliphatic aldehydes for the synthesis of 4-alkyl-6-amino- 3,5-dicyanopyridine-2(1H)-thiones

The condensation of aliphatic aldehydes with malononitrile and cyanothioacetamide gives 4-alkyl-2,6-diamino-3,5-dicyano-4H-thiopyrans which recyclize into 4-alkyl-6-amino3,5-dicyanopyridine-2(IH)-thiones. The latter are easily S-alkylated with α-haloacetonitriles and α-haloacetophenones.

ChemInform Abstract: Hindered Organoboron Groups in Organic Chemistry. Part 24. The Condensation of Aliphatic Aldehydes with Dimesitylboron‐Stabilized Carbanions to Give Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Hindered Organoboron Groups in Organic Chemistry. Part 25. The Condensation of Aliphatic Aldehydes with Dimesitylboryl‐Stabilized Carbanions to Give Alkenes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Hindered organoboron groups in organic chemistry. 24. The condensation of aliphatic aldehydes with dimesitylboron stabilised carbanions to give ketones.

The condensation of boron stabilised carbanions, Mes 2BCHLiR 1, (R 1≠H) with aliphatic aldehydes, R 2CHO, followed by treatment with trifluoroacetic anhydride (TFAA) or N-chlorosuccinimide (NCS) is an unique, broadly applicable redox process that yields ketones, R 1CH 2COR 2, directly and in high yields. The anion Mes 2BCH 2Li (Mes 2BCHLiR 1, R 1H) gives high yields of alkenes, R 2CHCH 2 in the same conditions.

Modified knoevenagel condensations. Synthesis of (E)-3-alkenoic acids.

Condensation of aliphatic aldehydes with a three molar excess of malonic acid and 0.001 mole of piperidinium acetate in refluxing xylene, with continuous removal of the water formed, gave almost exclusively (E)-3-alkenoic acids, in good yield (60–85%) and of high stereochemical purity (95–99%).

Pyrazolidine derivatives from the condensation reaction of hydrazobenzene with aliphatic aldehydes

The condensation reaction of hydrazobenzene with ethanal yields products of the pyrazolidine structure, III or V, according to whether it is carried out in the absence or presence of alcohols, respectively. Propanal reacts similarly to VIII while no reaction could be achieved with butanal. The structural evidence is based mainly on the mass and 1H NMR spectra which disprove the structures IV and VI, originally suggested by Rassow. The reaction is analogous to the condensation of aliphatic aldehydes with N-phenylhydroxylamine yielding 1,2-oxazolidine derivatives VII.

Derivatives of Coumaran. II. Condensation of Aliphatic Aldehydes and Ketones with 6-Methoxycoumaran-3-one. Reduction of 2-Isopropylidene-6-methoxycoumaran-3-one

Derivatives of Coumaran. II. Condensation of Aliphatic Aldehydes and Ketones with 6-Methoxycoumaran-3-one. Reduction of 2-Isopropylidene-6-methoxycoumaran-3-one