S. Grzejszczak

Organosulphur compounds—XVIII1: A new and general synthesis of ketene s,s- and o,s-thioacetals based on the horner-wittig reaction

Abstract A new and general synthesis of ketene S,S-thioacetals ( 1 ) and ketene O.S-thioacetals ( 6 ) which involves the Horner-Wittig reaction of carbonyl compounds with the metallated S,S- and O,S-thioacetals of formyl-phosphonates ( 4 and 5 ) is described. The Horner-Wittig reaction of 4 with aromatic aldehydes can be carried out under two-phase conditions. The generation of the carbanions from 4 and 5 as well as the course of their reaction with carbonyl compounds were studied by the low temperature 31 P NMR spectroscopy. It was found that S,S-thioacetals of formylphospbonates ( 4 ) are very easily metallated in contrast to O,S-thioacetals of formyl-phosphonates ( 5 ) which form the lithium derivatives only on treatment with t-butyllitnium. No evidence was obtained from 31 P NMR spectra supporting the formation of the lithium derivatives of 0,0-acetals of formyl-phosphonates ( 12 ).

Addition of elemental selenium to phosphonate carbanions- - a key step in the synthesis of vinylphosphonates. A new synthetic approach to 1,4-dicarbonyl systems.

Abstract A convenient synthesis of vinylphosphonates which involves addition of elemental selenium to phosphonate carbanions followed by alkylation and selenoxide elimination is described. A general approach to 1,4-dicarbonyl systems based on diethyl α-methylthiovinylphosphonate is also reported.

Conversion of 1,3- into 1,4-dicarbonyl compounds by means of α-phosphoryl sulphides. Total synthesis of dihydrojasmone and methylenomycin B.☆

An effective synthesis of 1,4-dicarbonyl systems involving the Horner—Wittig reaction of α-phosphoryl sulphides with the half-protected 1,3-dicarbonyl compounds followed by hydrolysis of the vinyl sulphides formed is described. The total synthesis of dihydrojasmone and methylenomycin B employing this approach is reported.

Synthesis of mono- and 1,4-dicarbonyl compounds based on the oxygenation of phosphonate carbanions. Synthesis of dihydrojasmone, allethrone and methylenomycin b☆

Abstract Oxidation of the α-alkylthio-substituted phosphonate carbanions was found to give the corresponding carbonyl compounds. A new synthesis of 1,4-dicarbonyl systems involving the oxygenation of phosphonate carbanions as a key step is described. Total synthesis of dihydrojasmone and allethrone and formal synthesis of methylenomycin B is reported.

α-Phosphoryl sulfoxides. VIII: Stereochemistry of α-chlorination of α-phosphoryl sulfoxides

Abstract Chlorination of α-phosphoryl sulfoxides 1 with iodobenzene dichloride and sulfuryl chloride in the presence and in the absence of pyridine and stereochemical investigations of this reaction using (+)-(S)-α-dimethoxyphosphorylmethyl p-tolyl sulfoxide 1a are described. It was found that conversion of 1 to the corresponding α-chloro-α-phosphoryl sulfoxides 2 occurs under the stereochemical control of the sulfinyl group and leads to diastereomeric mixtures. The extent of asymmetric induction at the α-carbon atom and racemization of the chiral sulfinyl centre in 1 depend on the reaction conditions. The structure of the major diastereomer formed in the chlorination of (+)-(S)-1ai.e. (+)-(S)c(S)s-α-chloro-α-dimethoxyphosphorylmethyl p-tolyl sulfoxide 2a was determined by X-ray analysis. The structure was solved by direct methods and refined to R=0.081. The experimental data on chlorination of α-phosphoryl sulfoxides 1 point to retention of the configuration at both chiral centres (C and S) and this stereochemistry can be rationalized assuming addition-elimination mechanism involving the formation of a positively charged ylide as intermediate.

Organosulphur compounds—IX: NMR and structural assignments in α,β-unsaturated sulphoxides using additive increments method

Abstract Additive shielding increments for the sulphinyl group, RS(O)-, have been estimated (ZRSO-gem 1·27; ZRSO-cis 0·67; ZRSO-trans 0·41) and their utility in making NMR structural assignments in α,β-unsaturated sulphoxides is presented.

Synthesis of Some Biologically Active Cyclopente-Nones using New Organophosphorus Reagents

Abstract The use of organic phosphorus and sulfur compounds in the general synthesis of biologically active functionalized cyclopentenones is presented.

Organosulphur compounds—XXIX : Synthesis and pummerer rearrangement of β-phosphoryl sulphoxides

Abstract β-Diethoxyphosphorylethyl sulphoxides 4 , prepared by selective oxidation of the corresponding sulphides 6 using bromine/potassium hydrogen carbonate as oxidising agent in a two-phase system, undergo the Pummerer rearrangement accompanied by elimination affording E-β-ethylthio-vinylphosphonate 7 . The synthesis of Z-α-bromo-β-ethylthiovinylphosphonate 14 is also described.

SYNTHESIS OF DISTYRYL SULPHIDES, SULPHOXIDES AND SULPHONES BY HORNER-WITTIG REACTION IN TWO-PHASE SYSTEM

Abstract A convenient method is described for the formation of distyryl sulphides, sulphoxides and sulphones. Thus, Horner-Wittig reaction in two-phase system of the corresponding phosphonates with aromatic aldehydes affords the desired α β unsaturated sulphur compounds. The geometry of compounds so formed was assigned with the aid of NMR spectroscopic methods.

Application of the additive increments method to the calculation of chemical shift of olefinic protons in aromatic olefines: Additive increments for para and meta substituents in the aromatic ring

Abstract Additive increments for para and meta substituents in the aromatic ring were calculated on the basis of 332 examples of chemical shifts and were correlated with Hammetts constants. Examples of calculation of chemical shifts of olefinic protons in substituted aromatic olefines by means of the increments are given.