M. Mladenova

Stereoselective approaches to (E,E,E) and (Z,E,E)-α-chloro-ω-substituted hexatrienes: Synthesis of all E polyenes

Abstract Two stereocontrolled synthetic approaches to (E,E,E) and (Z,E,E)-α-chloro-ω-substituted hexatrienes 1–3 are described starting from unsaturated compounds 4–6. The key step of the first approach is based on the palladium-catalyzed rearrangement of bis-allylic acetates 4 and 5 and the second one is based on the stereoselective reduction of homopropargylic alcohols 6 followed by an elimination reaction. These stable chlorotrienes 1–3 are suitable synthetic intermediates for the construction of navenone B and all E polyenes (trienes, tetraenes, hexaenes and heptaenes).

Chromatographic behaviour of diastereoisomers : VI. Relative retentions of the diastereoisomers of 3-hydroxy-2,3-diarylpropionates on silica gel and their theoretical interpretation

Abstract Separations by thin-layer chromatography on silica gel have been achieved for fifteen diastereoisomeric pairs of the type Ar—CH(X)—CH(COOR)—Ar′ (X = OH, OAC or NHPh; R = Me, iso-Pr, n -Bu, iso-Bu or tert .-Bu) which have known relative configurations. R F values of the compounds studied have been measured as a function of the concentration of diethyl ether in mixtures with heptane. Thus, the values of a parameter, related to the adsorption pattern, have been found. The relative retentions of the diastereoisomers R F ( erythro ) > R F ( erythro ) within those compounds where X = OH and R - tert .-Bu have been explained. Four different patterns of adsorption have been discussed. The data and the conclusions permit further outlining of the scope of each of the two retentions; they also support the previously elaborated criteria for thin-layer chromatographic assessment of the relative configurations of other diastereoisomeric pairs of tetrasubstituted ethanes.

An efficient stereocontrolled synthesis of functionalized chlorodienes and chlorotrienes

Abstract A stereoselective synthesis of ω-chlorodienals and ω-chlorodienones was described. Conjugated ω-chlorotrienals and trienones were also easily prepared via an efficient palladium-catalyzed rearrangement of allylic acetates.

An Efficient Synthesis of Enediyne and Arenediyne Lactams

Abstract Enediyne and arenediyne lactams are easily synthesized from (Z)-dichloroethylene and o-dibromobenzene.

A Convenient Synthesis of Aminoacids by ZnBr2 Promoted Reaction of Ketene bis(Trimethylsilyl) Acetals with Aldimines

Abstract The ZnBr2 promoted addition of ketene bis(trimethylsilyl) acetals to aromatic aldimines affords β-arylaminoacids in good to excellent yields. Under the same reaction conditions vinylic ketene bis(trimethylsilyl) acetals give exclusively or mainly δ - phenylaminoacids.

An Efficient Stereocontrolled Synthesis of Di-and Triunsaturated Carbonyl Compounds

Abstract ω-chlorodienals, ω-chlorodienones and 1,6-diacyl-1,3,5-hexatrienes were easily obtained from (E)-and (Z)-dichloroethylenes.

Addition of Lithium Reagents of N-Substituted Sulfonamides to Schiff Bases

Abstract Lithium reagents of N-substituted sulfonamides react with aromatic Schiff bases to give N-substituted amides of β-arylaminoethanesulfonic acids.

Structure du reactif d'ivanov et de quelques organometalliques issus des derives phenylacetiques—II : Stereochimie de la condensation avec la t-butyl-4 cyclohex-anone

Abstract Ivanov reagent and some other analogous reagents (phenyl acetique serie) have been condensed with t-Bu-4 cyclohexanone in order to complete investigation of the reactive species. In all the cases, equatorial attack is highly predominant; it let suppose that enolate, detected by NMR, is the reactive species.

Stereochemistry of the addition of α-metallated N,N-dialkylsulfonamides to aldehydes

Abstract The stereochemistry of aldol reactions of R1CH(M)SO2N(R)2 and aldehydes (R2CHO) is studied under a wide variety of reaction conditions. Effects of temperature, solvent, counterion and the effect of nature and effective volume of substituents R1 and R2 are investigated. These factors do not influence markedly the stereoselectivity of the reaction, which ranges from zero to moderate. A plausible transition state structure for the formation of β-hydroxysulfonamides is discussed.

Structure du reactif d'ivanov et de quelques organometalliques issus des derives phenylacetiques—I : Etude des solutions par rmn

Abstract Ivanov reagent add several analogous reagents (phenyl acetique serie) have been studied by NMR. In all the cases, an enolate-structure is revealed; no carbaneniate-species could be detected, even in very solvating solvents.