Vinylic substitution in the reaction of betulin diacetate with tert-butyl hypochlorite

Unlike unsaturated compounds containing alkyl groups at the double bond, low-temperature chlorination of betulin diacetate with tert-butyl hypochlorite involves mainly replacement of hydrogen in the vinylic position to give Z- and E-isomeric chlorides and a small amount of the allylic isomer, the latter resulting from elimination of hydrogen from the C³⁰H₃ group.     

Synthesis of indolines and tetrahydroquinolines fromortho-(alk-2-enyl)anilines

Intramolecular cyclization ofo-alkenylanilines was studied. Heating ofo-(cyclopent-2-en-1-yl) arylammonium chlorides at 200–220 °C yields cyclopenta[b]indolines as the main reaction products. Cyclization of 4-methyl-2-(pent-3-en-2-yl)aniline under the same conditions gave a mixture of indolines and tetrahydroquinolines. An alk-1-enylarylamine containing a vinylic double bond does not form cyclization products on the nitrogen atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 975–978, May, 1999.     

Synthesis of 2-nitrogenous derivatives of methyl (2E)-(2,3-dichloro-4-oxocyclopent-2-en-1-ylidene)acetate

Methyl (2E)-(2,3-dichloro-4-oxocyclopent-2-en-1-ylidene)acetate reacted with N-nucleophiles to give the corresponding 2-substituted derivatives via replacement of the vinylic chlorine atom according to the AdNE scheme.     

Résonance Magnétique Nucléaire. V.—Etude de Chlorures Vinyliques par RMN 1H. Incréments spécifiques des radicaux alkyle

Twenty five geometrical isomers of vinylic chlorides have been isolated and studied by ¹H n.m.r. and g.l.c; some of these have been chemically reduced for identification. New values of alkyl substituent increments for the estimation of olefinic proton chemical shifts are listed. The effect of chlorine (down field shift) on vinylic allylic and homoallylic protons is described, as well as the solvent effect of benzene (high field shift).     

Chiral (R)- and (S)-allylic alcohols via a one-pot chemoenzymatic synthesis

Chiral (R)- and (S)-allylic alcohols with an enantiomeric excess exceeding 99% have been prepared in good to high overall isolated yields through a two-step one-pot chemoenzymatic process based on the palladium-catalyzed Heck reaction of aryl iodides with butenone followed by an enzymatic reduction of the resultant vinylic substitution products. Alcohol dehydrogenases from Lactobacillus brevis and Thermoanaerobacter species were used to attain (R)- and (S)-stereoselectivity, respectively.     

Stereoselective synthesis of vinylic (Z)-vic-bis(arylchalcogenides)

Alkyne-titanium complexes 3, readily prepared in situ by the reaction of alkynes with Ti(O-i-Pr)₄/2 i-PrMgCl, react with electrophilic chalcogen species under mild conditions to provide the corresponding addition products in fair to good yields. The obtained vinylic vic-bis(arylchalcogenides) 4 are useful synthetic intermediates for introducing vinyl functions into organic molecules.     

Pentafluorophenyl complexes of cobalt(III) with 1-(diacetylmonoximatoimino)-3-(diacetylmonoximeimino)-propane (dotnH)

Cyclopalladation of vinylic oximes occurs for the sterically rigid oximes of 1-benzalcyclohexanone and 1-acetylcyclohexene giving dimeric complexes which retain the alkene double bond. The presence of the vinylic palladium bond is shown both by spectroscopic methods and cleavage reactions using carbon monoxide or cyanide ion. The complexes do not make good substrates for the synthesis of vinylic oxime derivatives.     

Mechanistic aspects of (CC) isomerization in vinylic rhodium(III) complexes

Observations concerning the (CC) isomerization of several vinylic Rh^III complexes suggest an intramolecular pathway; isomerization occurs at a rate which is affected by the backbonding ability of the metal and the π-acidity of the vinylic ligand in the complex.     

Cobalt-catalyzed electrochemical vinylation of aryl halides using vinylic acetates

The electroreduction of aryl halides (bromides or chlorides) allows the coupling reaction with vinylic acetates, in the presence of 2,2-bipyridine and catalytic amounts of cobalt bromide, leading to styrene derivatives in good yields.     

Synthesis and characterization of homochiral cholesteryl 1-alkenesulfinate esters

A number of ,β-unsaturated sulfinyl chlorides 1 has been separately prepared and treated with (−)-cholesterol under various conditions some of which incorporated chiral amines quinine or quinidine. Some (R_S) vinylic sulfinates could be isolated in enantiopure form following one or two recrystallizations of the resulting diastereomeric mixtures of (−)-cholesteryl 1-alkenesulfinates 2. Access to diastereomerically enriched (S_S) vinylic sulfinates (66–75% de) was achieved in three instances. Absolute stereochemical assignments were made with the assistance of the chiral solvating agent (R)-2,2,2-trifluoro-1-(9-anthryl)ethanol.     

Nucleophilic vinylic substitutions of (Z)-(2-aroyloxyvinyl)phenyl-λ-iodanes with tetrabutylammonium halides: vinylic SN2 reactions and ligand coupling on iodine(III)

Treatment of (Z)-(β-benzoyloxyvinyl)phenyl-λ³-iodanes, readily prepared from ethynyl(phenyl)(tetrafluoroborato)-λ³-iodane via stereoselective Michael-type addition of benzoic acids in methanol in the presence of sodium benzoates, with tetrabutylammonium halides in THF at 65 °C results in a vinylic S_N2 reaction to give the inverted (E)-β-benzoyloxyvinyl halides in high yields.     

Zur Kenntnis der Substitutionsprodukte der (2H)-Imidazol-4(3H)-thione und 2H-Imidazol-4(3H)-one

2H-Imidazole-4(3H)-thiones (a), available from methyl alkyl and methyl aryl ketones with sulfur and ammonia, react via their corresponding N-sodium compounds or in presence of tert. amines with alkyl and aryl carboxylic acid chlorides to give the corresponding intensely coloured (orange to violett) cryst. 3-acyl-2H-imidazole-4(3H)-thiones4 a-q and6–26. With dicarboxylic acid dichlorides the colourless cryst. N,N′-diacyl-bis-3-imidazoline-5-thiones5 a-d and27–32 are obtained. With carbamic acid chlorides and chloroformic acid esters the corresponding urea (33–35) and urethane derivatives36, 37 are formed. In an analogous way 2H-imidazol-4(3H)-ones react with acid chlorides to 3-acyl-2-imidazol-4(3H)-ones (44–50), which can also be obtained by treating the corresponding 3-acyl-2H-imidazole-4(3H)-thione with KMnO₄.     

Fused pyrimidine systems: XIV. Reaction of 2-alkenyl(alkynyl)sulfanylpyrido[3,4-d]pyrimidin-4(3H)-ones with arylsulfanyl chlorides

2-Allylsulfanylpyrido[3,4-d]pyrimidin-4(3H)-one reacted with arylsulfanyl chlorides in chloroform to give addition products to the exocyclic double bond, which were converted into linearly fused arylsulfanylthiazinopyridopyrimidines by the action of sodium acetate. The reactions of 2-allyl(cinnamyl, propargyl)sulfanylpyrido[3,4-d]pyrimidin-4(3H)-ones with arylsulfanyl chlorides in the presence of an equimolar amount of lithium perchlorate afforded angularly fused arylsulfanylmethylthiazolo- and -thiazinopyridopyrimidines.     

Regio-selective cyanation of (Z)-(1,2-dibromo-2-arylvinyl)triisopropylsilane with suppression of halogen elimination

Highly regio-selective cyanation of vicinal (Z)-dibromoalkenyl silanes was achieved by a vinylic Rosenmund-von Braun reaction, significantly suppressing side-production of alkyne. The alkyne was generated by a halogen elimination side-reaction that is an intrinsic problem in metal-activation of vicinal dihaloalkenes. We have studied to overcome the problem, and finally found the combination of CuCN and O = PPh₃ in toluene solvent effectively controlled the production of byproducts. The resultant single isomer has significance in potentially application as a multi-tunable synthetic scaffold.     

Rearrangement of polyarylene benzimidates into poly(N-arylenebenzamides)

The transformation of polyarylene benzimidates prepared by polycondensation of bisphenols with benzimidoyl chlorides in N-methyl-2-pyrrolidone into poly(N-arylenebenzamides) was studied.     

Multi-step reactions of N-monosubstituted (polyfluoroalkane)thioamides with alkyllithium reagents

Reactions of N-alkyl- or N-aryl(perfluoroalkyl)thiocarboxamides with alkyl lithium reagents are described. Trifluorothioacetamides are converted into the corresponding lithium salts. Compounds bearing a long polyfluorinated chain terminated by a CHF₂ group and compounds containing an N-alkyl substituent with a proton adjacent to nitrogen react further via a multi-step reaction sequence involving HF elimination and then vinylic fluorine substitution and/or S_N′ type fluorine substitution. These transformations led to unsaturated N-monosubstituted polyfluorinated thioamides.     

Effects of stereochemistry and β-substituents on the rates of vinylic SN2 reaction of hypervalent vinyl(phenyl)-λ-iodanes with tetrabutylammonium halides

Both stereoisomers of β-(2-phenylethoxy)vinyl-λ³-iodane and (Z)-β-aroyloxyvinyl-λ³-iodane were prepared stereoselectively. These substituted vinyl-λ³-iodanes undergo nucleophilic vinylic substitutions with n-Bu₄NX (X=Cl, Br, I) under mild conditions, yielding vinyl halides. The observed inversion of configuration at the ipso vinylic carbon atom is compatible with a concerted vinylic S_N2 mechanism. Kinetic measurements indicated that the rates for vinylic S_N2 reaction of (Z)-vinyl-λ³-iodane are greater than those of the E-isomer, probably because of the higher ground state energy of the Z-isomer. Electronic effects of β-substituents of vinyl-λ³-iodanes in the vinylic S_N2 reaction are also discussed.     

Facile synthesis of tetrahydro-1H-isoindolones via a sequential three-component copper-catalyzed coupling/propargyl-allenyl isomerization/[4 + 2] cyclization reaction

An interesting sequential three-component copper-catalyzed coupling/propargyl-allenyl isomerization/[4 + 2] cyclization reaction, providing a facile synthesis of highly substituted tetrahydro-1H-isoindolones from conjugated vinylic alkynes, imines, and α,β-unsaturated enoic acid chlorides is reported. The most attractive feature of this transformation is that three stereogenic centers could be generated in one step with high diastereoselectivity.     

Selectivity of acylation of ethanolamines with (meth)acryloyl chlorides

The selectivity with respect to N-acylation of the reactions of N,N-bis(2-hydroxyethyl)amine and N-methyl(2-hydroxyethyl)amine with acryloyl and methacryloyl chlorides was examined.     

Synthesis and desilylation of some bis(trimethylsilyl)alkenes and polymers bearing bis(silyl)alkenyl groups

The synthesis of various vinylbis(silanes) from some aryl and heteroaryl aldehydes and (Me₃Si)₃CLi in Et₂O is described. Friedel-Crafts reaction of 1,1-bis(trimethylsilyl)-2-(2-naphthyl)ethene with various acyl chlorides (RCOCl, R = Me, Et, i-Pr, i-Bu, n-pent) gave the corresponding α-silyl-α,β-unsaturated enones with high E steroselectivity. Moreover, poly(styrene)-co-[2,2-bis(trimethylsilyl)ethenyl(styrene)] obtained via the reaction of polymers bearing pendant enone functions and (Me₃Si)₃CLi, reacts with the same acyl chlorides in the presence of catalytic amount of AlCl₃ to give the new macromolecules bearing α-silyl-α,β-unsaturated enones and α,β-unsaturated enones.