Sequential reactions from catalytic hydroformylation toward the synthesis of amino compounds

Different families of new amino compounds were efficiently synthesized, through optimized sequential processes, involving rhodium catalyzed hydroformylation as the key step. The selection of appropriate hydroformylation catalytic systems and reaction conditions allowed obtaining aldehydes derived from several n-alkyl olefins, cholest-4-ene and 3-vinyl-1H-indole, which were subsequently transformed, in one-pot, in to α-amino acids via hydroformylation/Strecker reaction, and in to tertiary amines via hydroaminomethylation, with excellent yields.     

Phenylboronic acid mediated triple condensation reactions of phloroglucinol and unsaturated carbonyl compounds

[reaction: see text] A remarkable phenylboronic acid mediated triple condensation reaction of phloroglucinol (1,3,5-trihydroxybenzene) with a series of alpha,beta-unsaturated carbonyl compounds is reported. This experimentally simple reaction afforded novel C3-symmetric 2H-chromene derivatives. These derivatives represent structural analogues of the natural product xyloketal A, which has been reported to be a potent inhibitor of acetylcholine esterase.     

Reactions of diazoalkanes with unsaturated compounds 15. Catalytic reactions of unsaturated carbonyl compounds and their derivatives with diazomethane

The present study concerned with the influence of the nature of the acetal fragment in unsaturated compounds on the reactivity of the C=C bond in cyclopropanation reactions with diazomethane catalyzed by copper and palladium compounds. The acetal substituents at the α- or γ-position with respect to the C=C bond were found to exert an activating effect on the yields of cyclopropanation products compared to the starting unsaturated carbonyl compounds, which give 1,3-dipolar cycloaddition adducts with CH₂N₂ as by-products. Cyclopropanation of the double bonds appeared to be most efficiently catalyzed by Pd(acac)₂. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 979–983, April, 2005.     

ZnCl2 and CuCl promoted aldol reactions of isocyanoacetate with α,β-unsaturated carbonyl compounds

Reaction of ethyl isocyanoacetate with α,β-unsaturated carbonyl compounds was promoted by a stoichiometric amount of ZnCl₂ or a catalytic amount of CuCl/Et₃N (1:1) to give 5-alkenyl-4-carboethoxyoxazolines (3) in moderate yields. The oxazolines (3) were converted by palladium catalyst to 2-formamino-2,4-alkadienoic acid ethyl esters (5).     

Silver versus gold catalysis in tandem reactions of carbonyl functions onto alkynes: a versatile access to furoquinoline and pyranoquinoline cores

An efficient and versatile tandem process of acetalization and cycloisomerization reactions has been developed for the reactions of 1-alkynyl-2-carbonylquinoline substrates. The reaction occurs thanks to Au(I) and Ag(I) catalysis. Silver(I) catalysis has been extensively studied (11 different silver species) on a broad range of quinoline derivatives (variation of alkyne substituent, of carbonyl function and of nucleophiles), leading to a variety of furoquinoline and pyranoquinoline moieties. An insight is given for the presumed mechanism along with DFT-B3 LYP/6-31G** calculations to address the 6-endo and 5-exo regioselectivities observed.     

Isomeric composition of pyrazolines obtained from unsaturated carbonyl compounds and hydrazine

The ²-pyrazolines synthesized under the usual conditions from unsaturated aldehydes and hydrazine contain from 2 to 3% of the ¹-isomers and considerable amounts of the isomeric 3-alkyl-²-pyrazolines, which are formed as a consequence of migration of the double bond. Mixtures of the stereoisomeric ²-pyrazolines are formed from ,-dialkyl-substituted acroleins. Migration of the double bond does not occur in the condensation of unsaturated ketones with hydrazine, and ²-pyrazolines that are free from admixtures of the structural isomers are obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1225–1229, September, 1971.     

Sequential enolboration/hydroformylation/aldol addition: a new one-pot cascade reaction for the regio- and diastereoselective formation of carbocyclic quaternary centres from acyclic olefins

Starting from unsaturated carbonyl compounds a mild new cascade reaction involving enolboration, rhodium-catalysed hydroformylation and intramolecular aldol addition in a regio- and diastereoselective fashion leads to cyclic compounds containing highly-functionalised quaternary carbon centres.     

Scope of the reductive aldol reaction: application to aromatic carbocycles and heterocycles

The reductive aldol reaction of electron deficient aromatic compounds has been investigated and found to be a viable method for carbon-carbon bond formation. Reductions under ammonia and ammonia-free conditions were both capable of facilitating the aldol reaction although the latter showed more scope for reaction with enolisable aldehydes. Moreover, reduction under ammonia-free conditions allowed the addition of Lewis acids which improved stereoselectivity to favour the anti stereoisomer. Production of the syn diastereoisomer was possible through either one of two different protocols performed after partial reduction was complete. While the main emphasis of this paper concerns the reductive aldol reaction of electron deficient pyrroles, it was also shown that both benzenoid and furan aromatic compounds were amenable to such reducing conditions.     

Rearrangements in the formation of pyrazolines from alkyl hydrazines and unsaturated carbonyl compounds

The isomeric composition of the 2-pyrazolines obtained by the condensation of croton aldehyde and methyl vinyl ketone with C₁–C₄ monoalkyl hydrazines has been studied by the GLC method. It has been shown that in the reaction of croton aldehyde with isopropyl hydrazine, isobutyl hydrazine, and, to a smaller extent, with methyl hydrazine, in addition to the 1-alkyl-5-methyl-2-pyrazolines the 1, 3-isomers are formed. In other cases, only one pyrazoline, corresponding to the structure of the carbonyl compound, is formed. Eight previously-unknown dialkyl-2-pyrazolines are described.     

Sequential amination/annulation/aromatization reaction of carbonyl compounds and propargylamine: a new one-pot approach to functionalized pyridines

A general one-pot synthesis of pyridines 4a-t from the reaction of dialkyl acyclic/cyclic ketones 1a-i, methyl, aryl/heteroaryl ketones 1m-r, and aldehydes bearing alpha-hydrogens 1s,t with propargylamine 2 is described. Gold and copper salts are efficient catalysts for the reaction of ketones with 2. The formation of the pyridines 4 is suggested to proceed through the sequential amination of carbonyl compounds followed by regioselective 6-endo-dig cyclization of the N-propargylenamine (N-propargyldienamine) intermediate 3(5) and aromatization reaction. Whereas the preparation of linear polycyclic pyridine 4i can be carried out by reacting cholestan-3-one 1i with 2, the angular polycyclic pyridine 4j has been obtained starting from cholest-5-en-3-one 1j. Selectivity of the reaction of polycyclic dicarbonyls 1k,l with 2 has also been investigated.     

Hydrazine-1-carbonitriles: new synthesis approach to and reactions with carbonyl compounds

Abstract  

A series of 1-(pyrimidin-2-yl)hydrazine-1-carbonitriles was synthesized by base-catalyzed condensation of 3,4-diamino-1,2,4-triazole hydrobromide with several 1,3-dinucleophilic compounds. These final products were formed by ring opening of the 1,2,4-triazolium ring via intermediate 3-amino[1,2,4]triazolo[1,5-a]pyrimidinium bromides.     

A versatile and highly stereoselective access to vinyl triflates derived from 1,3-dicarbonyl and related compounds

1,3-Dicarbonyl derivatives, such as 1,3-diketones, beta-ketoaldehydes, beta-ketoesters, beta-ketoamides, beta-ketophosphonates and beta-ketosulfones were efficiently converted to the corresponding Z vinyl triflates with high stereoselectivity. Precoordination with lithium triflate in dichloromethane and enolization with mild bases such as trialkylamines or DBU followed by trapping with triflic anhydride probably accounted for such high selectivity, achieved even at 0 degrees C. This method offers the first direct route to vinyl triflates from beta-ketoamides, beta-ketophosphonates and beta-ketosulfones.     

Increased structural complexity leads to higher activity: peptides as efficient and versatile catalysts for asymmetric aldol reactions

[reaction: see text] Peptides containing a secondary amine and a carboxylic acid in a specific orientation to each other are presented as highly efficient catalysts for asymmetric aldol reactions: (1) their activity is considerably higher compared to that of proline, and (2) the enantioselectivity of the peptidic catalysts can be changed from (R)- to (S)-selectivity by simple modifications of the secondary structure.     

Boron enolates of a hydantoin chiral auxiliary derived from l-phenylalanine: a versatile tool for asymmetric aldol reactions

The aldol reactions of boron enolates derived from a hydantoin chiral auxiliary derived from l-phenylalanine occur in good yields with high syn diastereoselectivity. Aldol adduct 4a is readily cleaved by hydrolysis to afford (2S,3S)-3-hydroxy-2-methyl-3-phenylpropionic acid 5a in good yield and in almost enantiomerically pure form.     

Bismuth triflate-catalyzed oxa- and thia-Pictet-Spengler reactions: access to iso- and isothio-chroman compounds

A new route to functionalized iso(thio)chromans is described. The compounds are accessible easily in a one pot-reaction by using different benzaldehydes and phenylethanethiol or phenylethanol in presence of bismuth triflate.     

Direct, pyrrolidine sulfonamide promoted enantioselective aldol reactions of α,α-dialkyl aldehydes: synthesis of quaternary carbon-containing β-hydroxy carbonyl compounds

A procedure has been developed for direct, asymmetric aldol reactions of α,α-dialkyl aldehydes with aromatic aldehydes, which produces quaternary carbon-containing β-hydroxy carbonyl compounds. The processes, promoted by the organocatalyst (S) pyrrolidine sulfonamide, take place in high yields with exceptionally high levels of enantioselectivities.