Expedient synthesis of β,β-disubstituted α-methylenepropionates

Baylis-Hillman alcohols are excellent sources of the allylic halides ArCHCH(CH₂X)(CO₂R) (X=Br, Cl; R¹=Me, Et, Bu^t). The Z double bond isomers are attained in high isomeric purity (>14:1, Z/E). The halides are chemo- and regiospecifically transformed into the acrylates (ArCHR²)C(CH₂)(CO₂R¹) on treatment with Zn(R²)₂ (R²=Me, Et, CH₂TMS, CH₂SiMe₂OMe) or PrZnBr in the presence of catalytic amounts of copper(I) salts (0.5-20 mol%) in high yield.     

A Convenient Synthesis of β-Chloro, β-Methylthio α,β-Unsaturated Ketones from β-Oxodithioesters

The reaction of β-oxodithioesters with the Vilsmeier-Haack reagent prepared from POCl₃ and DMF provide β-chloro, β-methylthio α,β-unsaturated ketones in good yields.     

A,D-Oligomethylenic capping of α- and β-cyclodextrins

α- and β-cyclodextrins have easily been converted into basket molecules, the handle being an oligomethylenic chain bridging A and D positions on the primary rim. The size of the handle influences the complexing properties of these cyclodextrins. To cite this article: T. Lecourt et al., C. R. Chimie 6 (2003) 000–000.     

Reaction of 2-aminopyridines with α, β-unsaturated acids

The reaction of 2-amino- and 2-amino-5-halopyridines with acrylic, methacrylic, and crotonic acids forms N-(2-pyridyl)- and N-(5-halo-2-pyridyl)--alanines and the betaines 2-amino-1-(2-carboxylatoethyl)pyridinium or 3,4-dihydropyrido[1,2-a]pyrimidin-2-ones, or their homologs.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 80–85, January, 1992.     

The Synthesis of Substituted α, β-Butenolides from γ-Hydroxy-α, β-Acetylenic Esters

Abstract

The α, β-butenolide ring system is found in a number of physiologically important natural products² and there has been recent interest in the development of methods of synthesis of compounds of this type.³ It is well known that α, β-unsubstituted butenolides may be prepared by catalytic hydrogenation of γ-hydroxy acetylenic acids.^4,5b Recently, an excellent route of γ-hydroxy acetylenic esters which involves the addition of the lithium acetylide salts of propiolic esters to aldehydes⁵ and ketones⁶ has become available. We have carried out the addition of ethyl lithiopropiolate (1) to cyclohexanone (2) and 4-t-butylcyclohexanone (3) and wish to report the conversion of these adducts into corresponding β-methyl or β-methyl-α-allyl-α, β-butenolides.     

DABCO-catalyzed regioselective cyclization reactions of β,γ-unsaturated α-ketophosphonates or β,γ-unsaturated α-ketoesters with allenic esters

Highly efficient DABCO-catalyzed [4 + 2] cycloaddition of β,γ-unsaturated α-ketophosphonates or β,γ-unsaturated α-ketoesters with allenic esters gives the corresponding highly functionalized tetrahydropyran and dihydropyran derivatives in good to excellent yields and moderate to good regioselectivities under mild conditions.     

Diastereoselective α-Alkylation of β-Amino Esters: Preparation of Novel α-Substituted β-Amino Esters from α-Amino Acids

b-Amino acids and their derivatives have attracted considerable attention in recent years due to their occurrence in biologically active natural products, such as dolastatins 11, cyclohexylnorstatine 22 and taxol 33. bAmino acids also find application in the synthesis of blactams4, piperidines5, indolizidines6. Moreover, the peptides consisting of bamino acids, the so called bpeptides, have been extensively studied recently7. Consequently, considerable efforts have been directed to the synt…     

Radical Addition Reactions of α-Substituted β,β-Difluorovinyl Sulfones

The radical addition reactions of α-substituted β,β-difluorovinyl sulfones 1 with α-oxy and acyl radical species, such as 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, butanal and hexanal, afforded radical addition products 2--16 in good yields.     

Direct Synthesis of Amphiphilic α-, β-, and γ-Cyclodextrins

ABSTRACT

The clean one step synthesis of the amphiphilic α-, β-, and γ-cyclodextrins starting from per-(6-bromo-6-deoxy)-α-, -β-, and -γ-cyclodextrins is described. The role of the lipophilic tail is played by various aryl groups (phenyl, p-bromophenyl, p-O-butoxyphenyl, p-pentylphenyl, and o-, m-, and p-nitrophenyl) linked by a thioether bridge to the position C-6 of each glucopyranose unit. The yields of the S-alkylation reactions were very high (85-95%).     

Reactions of β-Sulfinyl α,β-Unsaturated Ketones with Dienes

β-Sulfinyl α,β-unsaturated ketones (2a-f) reacted in a regioselective manner with dienes such as butadiene (3a) and 1,3-pentadiene (3b) to give 1,4-cyclohexadiene derivatives (4-8) with the concomitant elimination of sulfenic acid, while the ketones (2a-c) reacted with cyclopentadiene (3c) to yield the norbornenes (9).     

Radical one-pot α,β-dual and β-mono-oxymethylation of alkylidenemalonate

Dimethylzinc-mediated radical conjugate addition reaction of dimethyl alkylidenemalonates with iodomethyl pivalate gave a high yield of the α,β-dual oxymethylation product in one pot under air and the β-pivaloyloxymethylation product under argon.     

Reactions of α-halo-α, β-unsaturated aldehydes with secondary amines

Reactions of 2-halo-2-alkenals R(R)C=CX-CHO with secondary amines R₂NH occur asipso-substitution of the halogen atom, along with fragmentation and condensation, yielding 1,2-diaminoethenes R₂NCH=CHNR₂, carbonyl compounds RC(O)R, 1,3-bis(amino)-2-haloolefins R(R)C(NR₂)CX=CHNR₂, and formamides R₂NCHO. The ratio between the competing reactions depends on the structure of the starting compounds and the experimental conditions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp, 135–138, January, I996.