Synthesis and stereochemistry of ω-azolylalkenes [1]

ω-Azolylalkenes 3, 4, and 5 were synthesized by N-alkylation of C-alkylation of ω-bromoalkenes 2, which were obtained either by phase transfer Wittig reactions of ω-bromoalkylphosphonium salts 1 with aldehydes or by Wittig reactions of ω-hydroxyalkylphosphonium salts 6 with aldehydes and subsequent bromination. ω-Azolylalkenes 3 were also directly prepared by the Wittig reaction of ω-azolylalkyltriphenylphosphonium salts 8 with aromatic aldehydes. The stereochemistry of these Wittig reactions was studied. © 1997 John Wiley & Sons, Inc.     

A Novel Synthetic Method for the Preparation of Aliphatic Aldehydes from the Corresponding Carboxylic Acids

A novel synthetic method for the preparation of aliphatic aldehydes from the corresponding carboxylic acids via 1,3‐dimethylbenzimidazolium salts is provided. 1,3‐Dimethylbenzimidazolium salts were rapidly reduced with sodium/ethanol and then hydrolyzed with hydrochloric acid to obtain aliphatic aldehydes, in which the 1,3‐dimethylbenzimidazolium salts can be readily achieved from the corresponding carboxylic acids. The mechanism for the reductive reaction of 1,3‐dimethylbenzimidazolium salts with sodium/ethanol was discussed.     

A New Route to Mercury-Containing Triphenylphosphonium Salts with Electron-Withdrawing Groups at the P Atom and Some Transformations of These Compounds

(Aroylmethyl)triphenylphosphonium salts react with mercury(II) trifluoroacetate with replacement of the labile methylene hydrogen atom by the HgOCOCF₃ group to give mercury-containing triphenylphosphonium salts in quantitative yields. Treatment of the mercurated salts with potassium carbonate yields mercury-containing triphenylphosphonium ylides of symmetrical and unsymmetrical structures, which enter Wittig reaction with aromatic aldehydes to form the corresponding mercurated olefins (Z isomers) and triphenylphosphine oxide.     

Pentaatomie heteroaromatic cations. Note III . A Convenient Synthesis of Aldehydes from Carboxylic Acids via 2-Substituted 1,3-Benzoxathiolium Perchlorates

A convenient method for the preparation of aldehydes from the corresponding carboxylic acids is presented. By reaction of the carboxylic acids with o-mercaptophenol and perchloric acid in phosphorus oxychloride, the corresponding 2-substituted 1,3-benzoxathiolium perehlorates were obtained. Reduction of the salts with lithium aluminium hydride in dry ether gave 2-substituted 1,3-benzoxathioles, which, when hydrolyzed by mercuric chloride, gave the corresponding aldehydes. Twenty five aldehydes of different structure were obtained in good yields, by a fast and simple procedure.     

Spiropyrans based on nitrogen heterocycles

The corresponding merocyanins (II and III), which are not capable of intramolecular cyclization to form spiropyrans, were obtained by the condensation of quaternary salts of 2- and 4-methylquinoline with o-hydroxyaryl aldehydes. In contrast to II and III, the products of the condensation of 5, 6-dimethylphenanthridinium salts with o-hydroxyaryl aldehydes (IV and V) exist, under the usual conditions, in the spiropyran form, while the derivative of 5-nitrosali-cylaldehyde can be isolated in both the cyclic and merocyanin forms. These differences are associated with the magnitude of the positive charge on the carbon atom which participates in closing the pyran ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 167–170, February, 1971.     

2-Styryl-4H-1,3-benzoxazin-4-onium salts

A method was developed for the synthesis of 2-styryl-4H-1,3-benzoxazin-4-onium salts by condensation of 2-alkylbenzoxazinonium salts with aromatic aldehydes. It is shown that these same compounds are formed by acid condensation of salicylamides, salicylnitrile, or salicylaldoxime with aromatic aldehydes in acetic anhydride. The hydrolysis and alcoholysis of the synthesized salts were studied.     

Synthesis and use of mono- or bisxylyl linked bis(benzimidazolium) bromides as carbene precursors for C-C bond formation reactions

Two benzimidazolium moieties linked by one or two xylyls (m- and p-) have been synthesized, characterized and then they were used for Heck coupling reactions as in situ formed catalysts. Mono bridged salts are more efficient as compared to bisbridged salts. In addition, mono bridged salts were converted to Rh-NHC complexes which were tested as catalysts for the arylation of aldehydes.     

Highly reactive equivalents of allylidenetriphenylphosphoranes for the stereospecific synthesis of 1,3-dienes by cis-olefination of hindered aldehydes

Ylides derived from 3-dimethylaminopropyltriphenylphosphonium salts react smoothly and stereospecifically with even hindered aldehydes to form $\text{Z}$-olefins which are easily converted to 1,3-dienes.     

Facile synthesis of highly substituted 3-aminofurans from thiazolium salts, aldehydes, and dimethyl acetylenedicarboxylate

[reaction: see text] A facile preparation of 3-aminofuran derivatives via multicomponent reactions of thiazole carbenes, aldehydes, and dimethyl acetylenedicarboxylate (DMAD) is reported. In this process, the thiazole carbenes, generated in situ from thiazolium salts, reacted with aldehydes and DMAD at -78 to 0 degree C in CH(2)Cl(2) to afford the substituted furans in moderate to good yields. Eight substituted thiazolium salts were employed as carbene precursors in the reaction. Besides aryl aldehydes, alpha,beta-unsaturated aldehydes, aliphatic aldehydes, and arenedial were also investigated and found to be applicable to this reaction.     

ON SOME INCORRECTNESS IN THE INTERPRETATION OF RESULTS OF THE REACTION OF SULPHINYLAMINES WITH ALDEHYDES

Abstract

In contradiction to reports by others, it was shown that sulphinylamines do not give products of cycloaddition on reaction with aldehydes in aprotic solvents. However, in the presence of a protonogenic agent, crystalline products were precipitated for which an ammonium α-aminosulphonate salt structure was confirmed. These salts are formed as a result of consecutive hydrolysis of sulphinylamines, condensation of aldehydes with the resulting amines, and bisulphite anion addition to Schiff bases.     

In situ generated rhodium‐based catalyst for addition of phenylboronic acid to aldehydes

New 1,3‐dialkylperhydrobenzimidazolinium and 1,3‐dialkylimidazolinium salts ( 2,4 ) as NHC precursors have been synthesized and characterized. These salts in combination with [RhCl(COD)]₂ provided active catalysts for the addition of phenylboronic acid to aldehydes under mild conditions. The in situ prepared three‐component system [RhCl(COD)]₂/imidazolinium salts ( 2,4 ) and KOBu^t catalyse the addition of phenylboronic acid to sterically hindered aldehydes affording the corresponding arylated secondary alcohols in good yields. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:461–465, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20132     

Cyclic sulfur ylides derived from Gleason-type chiral auxiliaries for the asymmetric synthesis of epoxy amides

Gleason-type chiral auxiliaries were used for the synthesis of a novel class of sulfonium salts, obtained via methylation of the sulfide with Meerwein's salt. The salts were reacted with aldehydes under basic conditions to provide epoxy amides, which were reduced to their corresponding epoxy alcohols in excellent enantiomeric excesses. Interestingly, it was feasible to synthesize both enantiomeric epoxy alcohols depending on which of the sulfonium salts, prepared from L-amino acids (6 and 9 from L-valine or 15 and 16 from L-serine) was employed.     

Reactions of substituted furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with benzothiazolium salts

A series of new push-pull compounds were synthesised by reaction of 5-aryl- furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with benzothiazolium salts. These new condensation products represent highly conjugated systems that have potential biological activity. The reaction of furo[b]pyrrole type aldehydes with benzothiazolium salts give potential precursors of cyanine dyes.     

Reaction of aldimine anions with vinamidinium chloride: three-component access to 3-alkylpyridines and 3-alkylpyridinium salts and access to 2-alkyl glutaconaldehyde derivatives

N-tert-Butylimino derivatives of aldehydes were deprotonated with LDA and reacted with vinamidinium chloride to give 2-alkylaminopentadienimine derivatives, which were isolated as their corresponding hydrochloride in 68-81% yield. Reaction of these derivatives with ammonium acetate or salts of primary amines, in n-butanol at 80 degrees C, afforded the corresponding 3-alkylpyridines or 3-alkylpyridinium salts in high yield. Alkaline hydrolysis of 2-alkylaminopentadieneimine derivatives allowed a practical accesss to potassium salts of 2-alkylglutaconaldehyde.     

Highly efficient synthesis of spirocyclic (1R)-camphor-derived triazolium salts: application in the catalytic asymmetric benzoin condensation

New (1R)-camphor-derived triazolium salts, incorporating a spirocyclic system, are described. Benzoin condensation of aromatic aldehydes, mediated by these salts affords α-hydroxyketones in good yields and moderate enantiomeric excesses.     

Transition-metal-catalyzed formation of trans alkenes via coupling of aldehydes

[reaction: see text] Rh(2)(OAc)(4) catalyzed the formation of exclusively trans fluorinated alkenes from aldehydes and pentafluorobenzaldehyde tosylhydrazone salts, which were readily prepared from pentafluorobenzaldehyde using the Bamford-Stevens reaction. A series of pentafluorophenyl-containing alkenes were synthesized from aldehydes in moderate to good yields under mild reaction conditions in a one-pot reaction. It is the first report of coupling two different aldehydes to form exclusively trans alkenes.     

Asymmetric epoxidation of olefins catalyzed by chiral iminium salts generated in situ from amines and aldehydes

[reaction: see text] A new approach for catalytic asymmetric epoxidation of olefins was developed that utilized chiral iminium salts, generated in situ from chiral amines and aldehydes, as catalysts. Epoxidation reactions can be conducted with 20 mol % of amines and aldehydes. The enantioselectivity of epoxides can be up to 65%. This modular approach obviates the difficulties inherent in the preparation and isolation of unstable exocyclic iminium salts.     

Novel hexadentate imidazolium salts in the rhodium-catalyzed addition of arylboronic acids to aldehydes

Four novel hexadentate imidazolium salts were synthesized from hexakis(bromomethyl)benzene and 1-substituted imidazole. The arylation of aldehydes with arylboronic acids was effected conveniently and in high yields by a catalyst system generated in situ from these hexadentate imidazolium salts, [Rh(COD)Cl]₂ and a base.     

(Z)-Selective Wittig and Corey-Chaykovsky reactions of propargyl ylides using trialkylgallium bases

Trialkylgalliums deprotonated propargylphosphonium salts and propargylsulfonium salts to form propargyl ylides. The resulted organogallium intermediates underwent the Wittig reaction and the Corey-Chaykovsky reaction with aldehydes giving (Z)-enynes and (Z)-epoxides predominantly. The use of an appropriate trialkylgallium is essential for the stereoselectivity.     

Synthesis of 4-ethoxyflavylium salts and flavones

4-Ethoxybenzopyrylium salts, which are converted to the corresponding flavones in quantitative yields by refluxing with water, were synthesized by condensation of o-hydroxyacetophenones with aromatic aldehydes in the presence of ethyl orthoformate and 70% perchloric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 187–190, February, 1977.