On the regioselectivity of elimination reactions in terpene derivatives

Tertiary alcohols with prenyl or geranyl moities, bearing a second oxygen. function in the 3, 4 or 5 position were dehydrated under various conditions : the composition of the olefinic mixture obtained was accounted for, by an intramolecular base relay effect.Basic elimination of analogous dimethylsutfonium salts gave results that could be related to the inductive effect : a correlation between regioselectivity and the Taft constantσ_I of the second oxygen function was found, except for the very basic alkoxide groups where an alternative regioselective elimination took place.     

Influence of substituents on regioselectivity of vinyllithium formation with acrylic acid Derivatives

β-Alkoxy, β-dialkylamino, and β-N-alkylacylamino substituents determine the regioselectivity of the vinylic deprotonation of acrylic ester and nitrile derivatives: either α- or β-vinyllithium species may be generated. The corresponding acrylamides or systems with additional α-alkyl or α-methylmercapto substituents are lithiated at β-position.     

Michael reactions of titanium enolates of glycolic acid derivatives with the Weinreb and morpholine amides of acrylic acid

The conjugate additions of titanium enolates of glycolate-derived chiral oxazolidin-2-ones to various Michael acceptors have been evaluated as an entry to enantiopure 1,2,5-trioxygenated and related synthons. alpha,beta-unsaturated Weinreb and morpholine amides do react under suitable conditions and their adducts can be converted to diverse C1-C5 chiral fragments.     

Copolymerization of acrylic acid with new acrylamide derivatives

Radical copolymerization of acrylic acid with acrylamide derivatives was studied. The cooplymerization constants were determined, and their dependence on the structure of the substituent in the acrylamide molecule and on the molecular weight of the polymers prepared was examined.     

Reaction of sulfur pentafluoride chloride with acrylic acid derivatives

Conclusions Sulfur pentafluoride chloride adds readily to acrylic acid derivatives to give derivatives of 1-chloro-2-pentafluorothiopropionic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. l, pp. 197–198, January, 1989.     

Electronic regioselectivity in the reactions of pyridinium ylides with tetracyanoethylene

Highly regioselective reactions of pyridinium ylides with tetracyanoethylene occur via an Ad_N-E mechanism to form Z-isomers of 3-aroyl-3-(1-pyridinio)-1,1,2-tricyano-2-propenides-1, corresponding in structure to 1,4-ylides with maximum charge separation. If the unsaturated nitrite starting material contains a nucleofugal group 1,2-elimination predominates over 1,3-elimination.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1087–1094, August, 1991.     

Chemo- and regioselectivity in the reactions of polyfunctional pyrroles

The chemo- and regioselectivity of the reduction, oxidation and Wittig reaction of polyfunctional pyrroles, containing a variety of reactive centres was investigated. The reaction of 3,5-dichloropyrrole-2,4-dicarboxaldehydes with potassium permanganate leads to regioselective oxidation of the 2-formyl group, while the Wittig reaction with 1 equiv of a triphenylphosphorane produced the 2-alkenyl substituted pyrroles.     

The diene synthesis with sulfur-containing derivatives of acrylic acids

Reaction of aqueous solutions of salts of acrylic acids with thioepi chlorohydrin affords thietyl acrylates, which on hydrolysis give 3-hydroxythietane, and on oxidation with hydrogen peroxide give 3-hydroxythietane 1,1-dioxide. The diene synthesis was carried out with these acrylates, and also with acryloyl and methacryloyl isothiocyanates.The authors thanks M. I. Mironova for the IR spectra and the elemantal analyses.     

Kinetics of reactions of derivatives of bischloromethylphosphinic acid with amines

Conclusions The authors have made a kinetic study of nucleophilic replacement of chlorine by an amino group in derivatives of bischloromethylphosphinic acid. The process takes place by an S_N1-mechanism in the case of weak nucleophilic reagents (the aniline type) and by an S_n2-mechanism in the case of strong nucleophilic reagents (benzylamine type).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 175–177, January, 1969.     

The production of episulfonium complexes from propylene and the regioselectivity of their reactions with nucleophiles

Conclusions The regioselectivity of the reactions of stable S-arylsulfonium complexes prepared from propylene and various nucleophiles corresponds to Markovnikov addition and the degree of selectivity of this reaction depends on the nature of the aromatic substituent. The episulfonium complexes prepared were characterized by¹³C NMR spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 563–572, March, 1979.     

Highly diastereoselective nitroaldol reactions with chiral derivatives of glyoxylic acid

N-Glyoxyloyl-(2R)-bornane-10,2-sultam (1a) and (1R)-8-phenylmenthyl glyoxylate (1b) react stereoselectively with simple nitroalkanes giving diastereomeric nitroalcohols with high asymmetric induction. The glyoximide 1a is proved to be a highly efficient chiral inducer, superior to glyoxylate 1b. In all cases, the absolute configuration (2S) and relative configuration, syn for the major diastereoisomers, were confirmed.     

Divergent regioselectivity in the base-promoted reactions of cyclic eight-membered alpha-ketols with activated halides

[reaction: see text] Deprotonation of 2-hydroxycyclooctanone followed by exposure to an allylic or benzylic halide proceeds very selectively to give the product of C-alkylation. The effect of Delta(5,6)-unsaturation is to promote instead the formation of the O-alkylated derivative. This crossover in kinetic preference is attributed to an inability of the olefinic system to attain a conformation conducive to proton abstraction at C-2.     

Ring enlargement reactions of tetramic acid derivatives

The 4‐hydroxypyridones 7 and 3‐hydroxypyridones 8/9 (azagrevellins) were prepared by reaction of the pyrrolidinetrione 4 and diazoalkanes. The ring enlargement proceeded by anionotropic [1,2]‐rearrangement introducing carbon between C‐3 and C‐4 or, to a lesser extent, between C‐2 and C‐3 due to the different migration aptitudes of the two acyl groups involved. In a cognate manner ring expansion between C‐2 and C‐3 occured by the interaction of diazomethane and the pyrrolidinetrione hydrazone 15 , to give the spiroe‐poxide 16 as the final product. From the reaction of trione 4 and diazomethane, however, the diepoxide 14 was obtained. In this case ring homologation must have taken place by insertion of carbon between C‐4 and C‐5. In a two step ring expansion the pyridones 21 and 22 were obtained from the maleineimides 17.     

The reactions of hexachlorocyclotriphosphazatriene with pyridine derivatives

The reactions of hexachlorocyclotripho‐sphazatriene, N₃P₃Cl₆ ( 1 ), with 2‐hydroxypyridine ( 2 ), 2‐aminopyridine ( 3 ), 2‐amino‐6‐methyl‐pyridine ( 4 ), and 2‐hydroxy‐4‐methylquinoline ( 5 ) have been investigated. The products were identified by elemental analyses, IR, ¹H, ¹³C, and ³¹P NMR spectroscopy. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:57–60, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20185     

Understanding the regioselectivity in Scholl reactions for the synthesis of oligoarenes

A short reaction sequence leads to oligoarene derivatives utilising a regioselective Scholl reaction for the unprecedented cyclisation to the mono-functionalised oligoarene under methanol elimination. Quantum-chemical investigations reveal the reason for the remarkably high regioselectivity.     

Rate constants for the reactions of methylvinyl ketone,methacrolein, methacrylic acid,and acrylic acid with ozone

Rate constants for the reaction of ozone with methylvinyl ketone (H₂C(DOUBLEBOND)CHC(O)CH₃), methacrolein (H₂C(DOUBLEBOND)C(CH₃)CHO), methacrylic acid (H₂C(DOUBLEBOND)C(CH₃)C(O)OH), and acrylic acid (H₂C(DOUBLEBOND)CHC(O)OH) were measured at room temperature (296±2 K) in the presence of a sufficient amount of cyclohexane to scavenge OH-radicals. Results from pseudo-first-order experiments in the presence of excess ozone were found not to be consistent with relative rate measurements. It appeared that the formation of the so-called Criegee-intermediates leads to an enhanced decrease in the concentration of the two organic acids investigated. It is shown that the presence of formic acid, which is known to react efficiently with Criegee-intermediates, diminishes the observed removal rate of the organic acids. The rate constant for the reaction of ozone with the unsaturated carbonyl compounds methylvinyl ketone and methacrolein was found not to be influenced by the addition of formic acid. Rate constants for the reaction of ozone determined in the presence of excess formic acid are (in cm³ molecule⁻¹ s⁻¹): methylvinyl ketone (5.4±0.6)×10⁻¹⁸; methacrolein (1.3±0.14)×10⁻¹⁸; methacrylic acid (4.1±0.4)×10⁻¹⁸; and acrylic acid (0.65±0.13)×10⁻¹⁸. Results are found to be consistent with the Criegee mechanism of the gas-phase ozonolysis. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 769–776, 1998