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.     

Epoxidation of unsaturated carbonyl compounds

Russian Journal of Organic Chemistry - Epoxidation of unsaturated carbonyl compounds by reaction with chloromethyl propargyl(allyl) ether in the presence of an alcoholate occurs exclusively at the...     

Nickel-catalyzed cycloaddition of unsaturated hydrocarbons and carbonyl compounds

A mild and general route for preparing pyrans and dienones from carbonyls and diynes is described. Ni imidazolylidene complexes were used to mediate cyclizations between diynes and aldehydes. The reaction of an enyne and an aldehyde afforded a mixture of cyclized products. In addition, a spiropyran was prepared from the cycloaddition of a diyne and cyclohexanone. [reaction: see text]     

The electronic structure of polyenes and unsaturated carbonyl compounds

PE spectra of polyene aldehydes are reported and discussed on the basis of a semiempirical LCFO-MO treatment within the π electron approximation. The necessary parameter values including the CC bond alternation were obtained by fitting PPP orbital and transition energies to the PE and UV data of diphenyl polyenes and polyene aldehydes. Thus, for planar systems the assignment of a PE band near 13.5 eV to the π orbital of the CO group could be given, which could be confirmed by the LCFO-MO calculations and by results from ab initio calculations, and which forms the basis of a discussion and comparison of π orbital interactions in planar unsaturated carbonyl compounds and hydrocarbons.     

Structures of the pyrazolines obtained from tiglic aldehyde and methylhydrazine

Using gas-liquid chromatography and PMR spectra, it is shown that condensation of tiglic aldehyde and methylhydrazine gives, in addition to the corresponding methylhydrazone, a mixture of stereoisomeric, 1,4, 5-trimethyl-²-pyrazolines and 1,3, 4-trimethyl-²-pyrazoline. Thus the reaction of formation of pyrazolines from unsaturated carbonyl compounds and hydrazines is not stereospecific and may involve hitherto unknown rearrangements.     

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.     

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.     

Structure and conversions of the condensation products of phenols with unsaturated carbonyl compounds

The reaction of 3,4-xylenol with crotonaldehyde leads to the formation of 2, 6, 7-trimethyl-4-(4, 5-dimethyl-2-hydroxyphenyl)chroman, whose structure is verified by IR and UV spectra, by the synthesis of the methyl and the benzoyl esters, and by the investigation of the conditions and the products of pyrolisis.The IR spectrum of a paste of IV in vaseline oil was recorded on a IKS-14 apparatus     

Reasons for the formation of pyrazolines of anomalous structure from unsaturated aldehydes

It is shown by gas-liquid chromatography and PMR spectroscopy that the reaction of alkylhydrazines with -alkylacroleins, as distinct from the -alkyl derivatives, results only in the formation of the normal products (1,4-dialkyl-²-pyrazolines or the corresponding -alkylacrolein alkylhydrazones). The latter isomerize on moderate heating with a catalytic amount of hydrochloric acid, the terminal C=C bond migrating to the middle of the chain to give , -dialkylacrolein or trialkylacrolein hydrazones rather than the expected cyclization products, 1, 4-dialkyl-²-pyrazolines. Condensation of isopropylhydrazine with -methyl--ethylacrolein and cyclization of -methyl--ethylacrolein isopropylhydrazone under forcing conditions gave the pyrazoline of anomalous structure, 1-isopropyl-3-ethyl 4-methyl-²-pyrazoline, without any of the expected 1-isopropyl-4-methyl-5-ethyl-²pyrazoline. The opinion is expressed that the formation of the pyrazoline with the anomalous structure is due to addition of the NH group of the hydrazine to the carbonyl group of the unsaturated aldehyde, which is sterically more accessible to the NH group than is the -substituted C=C bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1249–1254, September, 1970.     

Structure and conversions of the condensation products of phenols with unsaturated carbonyl compounds

The reaction of 3,4-xylenol with crotonaldehyde leads to the formation of 2, 6, 7-trimethyl-4-(4′, 5′-dimethyl-2′-hydroxyphenyl)chroman, whose structure is verified by IR and UV spectra, by the synthesis of the methyl and the benzoyl esters, and by the investigation of the conditions and the products of pyrolisis.     

Sequential hydroformylation/aldol reactions: versatile and controllable access to functionalised carbocycles from unsaturated carbonyl compounds

Three different modes of hydroformylation/aldol reaction sequences involving either acid-catalysed aldol reactions, Mukaiyama aldol addition of pre-formed enolsilanes or aldol addition of in situ generated boron enolates can be applied to unsaturated ketones and ketoesters to afford the corresponding carbocyclic aldol adducts in good yields proceeding through the intermediate activated ketoaldehydes. In selected cases, complimentary, synthetically useful diastereoselectivities were observed in the products.     

Conjugate addition of arylsilanes to unsaturated carbonyl compounds catalyzed by rhodium in air and water

ArSiCl3 and Ar2SiCl2, believed to be unstable in aqueous media, reacted efficiently with alpha,beta-unsaturated ketones and esters in air and water (in the presence of sodium fluoride and a rhodium catalyst), giving good to excellent yields of the desired conjugate addition products.     

A novel catalytic decarbonylative Heck-type reaction and conjugate addition of aldehydes to unsaturated carbonyl compounds

A novel rhodium-catalyzed decarbonylative reaction of aldehydes with unsaturated carbonyl compounds was discovered to generate Heck-type reaction product and conjugate addition product.     

Systematic synthesis of phthalimide-protected unsaturated hydrazine heterocycles

A four-step route for the synthesis of novel phthalimide-protected hydrazine heterocycles that include a C?C double bond in the cycle was developed. Phthalimide-protected Boc-hydrazine was used as a starting material, which was alkylated with bromoalkenes in mild conditions. Further steps involved Boc-deprotection and second alkylation with bromoalkenes. Finally, the heterocycles were produced by ring-closing metathesis. This route allows access to these versatile building blocks without using electrophilic amination or nitrosylation, therefore, significantly reducing environmental and safety concerns. Phthalimide-protected heterocycles can be derivatized further by modifying the carbon–carbon double bond and by deprotection and subsequent functionalization of the primary amino group. During the current research, various five- to seven-membered hydrazine heterocycles and numerous novel intermediate compounds were synthesized and thoroughly characterized.