S.-O. Lawesson

Studies on organophosphorus compounds—XXVIII: Syntheses of 3H-1,2-dithiole-3-thiones and 4H-1,3,2,-oxazaphosphorine derivatives from the dimer of p-methoxyphenyl-thionophosphine sulfide and der

Abstract Unsubstituted and 2-monosubstituted 3-oxo esters react with the dimer of p -methoxyphenyl-thionophosphine sulfide ( 1 ) and elemental sulfur in anhydrous toluene at 110° to give the corresponding 3H-1,2-dithiole-3-thiones ( 2 ) in nearly quantitative yields (90–95%). Ethyl 2,2-dimethyl 3-oxo-butanoate, failing to react in toluene at 110°, decomposes into a complex mixture at 140° in anhydrous xylene. Also secondary and tertiary 3-oxo-amides such as acetoacetanilide and N,N-dimethylacetoacetamide produce the corresponding 3H-1,2-dithiole-3-thiones ( 2 ) upon treatment with 1 and elemental sulfur. Primary 3-oxo-amides and 3-oxo-nitriles react with 1 in anhydrous toluene at 110° giving in all cases investigated, derivatives of 2,3-dihydro-2(4-methoxyphenyl)-4H-1,3,2-oxazaphosphorine-4-t as main products (70–95%). 1 H, 13 C and 31 P NMR data are tabulated and reaction mechanisms are suggested.

Studies on organophosphorus compounds—XXVII: Synthesis of thiono-, thiolo- and dithiolactones

Abstract Unsubstituted and alkyl- or cyanosubstituted lactones such as dihydro-2(3 H)-furanone, dihydro-5-methyl-2(3 H)-furanone, dihydro-5,5-dimethyl-4-propyl-2(3 H)-furanone and tetrahydro-2,2-dimethyl-5-oxo-3furan-carbonitrile react with the dimer of p-methoxyphenylthionophosphine sulfide, 1, in anhydrous xylene or toluene to give the corresponding thionolactones, 3a-d, in good yields. Dihydro-2(3 H)-thiophenone and 1 produce dihydro-2(3 H)-thiophenthione. Aromatic lactones such as 2 H-1-benzopyran-2-one give the corresponding 2-thione. 1-Oxa-4-thiaspiro[4,5]decan-2-one, when treated with 1 at 120-125°, gave 1,4-dithiaspiro[4,5]decan-2-one and 1,4-dithias-piro[4,5]decan-2-thione. Tetrahydro-5,5-dimethyl-2-oxo-4-propyl-3-furancarboxylic acid ethyl ester reacted with 1 at 110° giving the corresponding 2-thione and 5,5-dimethyl-4-propyl-4,5-dihydrothieno[2,3-c]-1,2-dithiole-3-thione.

Studies on organophosphorus compounds—XL: Reactions of ketones with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide☆

Abstract Cyclohexanone and cyclopentanone react with 2,4 - bis - 4 - methoxyphenyl) - 1,3,2,4 - dithiadiphosphetane 2,4-disulfide (lawesson Reagent ( LR ) at 80° with formation of new spiro - 1,3,5,2 - trithiaphosphorines 1 and 2 , respectively. 2-Methyl and 2-phenylcyclohexanone also react with LR at 80° producing the enethiols 3 and 4 , which on storage are transformed into the sulfides 5 and 6 . Unsaturated cyclohexanones 7–9 are transformed into the corresponding thioketones 10–12 after reactions with LR at 60° for a few hours. 2-Hydroxyketones react with LR with formation of 1,3,2-oxathiaphospholes and similarly a 2-aminoketone gave a 1,3,2-thiazaphosphole. Aromatic ketones, reacted with LR to give corresponding thioketones. Thiofluorenone dimerized to form the cyclic disulfide 31 , as proved by X-ray analyses.

Studies in mass spectrometry—XV : Mass spectra of sulphoxides and sulphones. The formation of CC and CO bonds upon electron impact☆

Abstract Although dialkyl sulphoxides and sulphones behave relatively simply upon electron impact, aromatic sulphoxides and sulphones show a pronounced tendency to undergo CO bond formation, as evidence by a number of decomposition pathways which involve the elimination of carbon monoxide. For example, dibenzothiophene dioxide (XV) decomposes from its molecular ion by successive eliminations of carbon monoxide.

Studies on amino acids and peptides—I : Synthesis of N-benzyloxycarbonylendo-thiodipeptide esters

Abstract N-Benzyloxycarbonylendothiodipeptide esters, 3, are synthesized without racemization from the corresponding N-benzyloxycarbonyldipeptide esters, 2, using 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide, 1, as thionation reagent. The benzyloxycarbonyl amino-protecting group (Z) is removed from 3 by using HBr-AcOH.

Studies on organophosphorus compounds XLVII preparation of thiated synthons of amides, lactams and imides by use of some new p,s-containing reagents☆

Abstract The thionation properties of 2,4-bismethylthio-1,3,2,4-dithiadiphosphetane 2,4-disulfide, 1 , 2,4-bis(4-phen-oxyphenyl)-1,3,2,4-dithiaphosphetan is that 2 , 3 and thionate most amides and lactams In THF at room temperature (reaction time 5 min) to give the corresponding thionated compounds. Imides are easily thionated by 2 , 3 and 4 In DME at 60 °C. The reactions of 1 with amides, imides and most lactams are run at 60°C to give good yields of the corresponding thionated compounds.

Preparation and alkylation of substituted β-hydroxydithiocinnamic acids

Abstract A number of substituted β-hydroxydithiocinnamic acids have been prepared. By use of so-called ion-pair extraction technique a general method has been found for the preparation of β-hydroxydithiocinnamic esters in high yields. From these esters both symmetrical and unsymmetrical ketene mercaptals have been synthesized, and in some cases thio-Claisen rearrangement and subsequent ring-closure reactions have been observed.

The transformation using the soft NO⊕-species

Abstract The reaction of NaNO2 in acidic solution with thiocarbonyl compounds has been studied. Secondary- and tertiary thioamides, 1-benzyl-hexahydro-2H-azepine-2-thione, 5-ethyl-5-phenyl thiobarbituric acid, certain thiourea derivatives, 2H-1-benzopyran-2-thione, O,O-diphenyl-thiocarbonic ester, O,S-diphenyl-dithiocarbonic ester, N,N-dimethyl-S-phenyl-dithiocarbamatic ester, N-ethyl-N-phenyl-O-ethyl-thiocarbamatic ester are all converted into the corresponding carbonyl-analogues. 4,4′-Bis (dimethylamino)-thiobenzophenone (Michlers thioketone) gives 3-nitro-4,4′-bis (dimethylamino)-benzophenone at room temperature. At (−10 °C)-(−5 °C) the expected oxo compound is obtained as the main product together with 4-(N-nitroso-methylamino)-4′-(dimethylamino)-benzophenone.

Synthesis, rearrangements, and fragmentation of ketene mercaptals derived from ketones or β-diketones and carbon disulphide

Abstract By use of the ion pair extraction technique, tetrabutylammonium salts of acetylacetone, benzoylacetone, and dibenzoylmethane were reacted with carbon disulphide to give salts of dithioacids. Alkylation gave dithioesters and ketene mercaptals. A simple procedure for the preparation of 2-diacylmethylene-1,3-dithietanes was found. Cyclisation reactions of some acetylacetone derivatives gave a 1,3-dithiolane, a mercaptothiophene, and a [2.3-b] thienothiophene. Allylic ketene mercaptals derived from acetone, cyclohexanone, acetylacetone, benzoylacetone, and dibenzoylmethane rearranged to α-allyl-dithioesters. Inversion of the migrating allyl group was observed when the ketene mercaptal had a vinylic hydrogen; otherwise retention was found. 3-[(Crotylthio-, methylthio-)methylene] acetylacetone underwent decomposition at 170° to methyl, 1-methyl-allyl sulphide and the “desaurin”: 2,4-bis-(diacetyl-methylene)-1, 3-dithietane. By-products in syntheses of the dithioesters and ketene mercaptals included trithiocarbonates, alkylated β-diketones, and compounds formed by reactions of the solvent (CH 2 Cl 2 ) with β-diketones or their carbon disulphide adducts (1,3-di-thietanes).

Studies in mass spectrometry—XVII : Rearrangement processes in some esters containing unsaturated linkages—the elimination of CO2 from esters☆

Abstract The mass spectra of a variety of propiolate, acetylenedicarboxylate, maleate, fumarate and cyanoacetate esters have been measured. The formation of ions via the elimination of carbon dioxide (with or without the associated loss of other groups) is quite common in these esters. The prevalence of such fragmentation processes, which are of obvious importance with respect to the element-mapping technique, is probably associated with the presence of double or triple bonds (in the vicinity of the ester function) which may be ionized by removal of an electron and thus provide an electron deficient site to which a group (alkyl, alkenyl, etc.) may migrate.Abstract The mass spectra of a variety of propiolate, acetylenedicarboxylate, maleate, fumarate and cyanoacetate esters have been measured. The formation of ions via the elimination of carbon dioxide (with or without the associated loss of other groups) is quite common in these esters. The prevalence of such fragmentation processes, which are of obvious importance with respect to the element-mapping technique, is probably associated with the presence of double or triple bonds (in the vicinity of the ester function) which may be ionized by removal of an electron and thus provide an electron deficient site to which a group (alkyl, alkenyl, etc.) may migrate.