Studies in mass spectrometry—XV Mass spectra of sulphoxides and sulphones. The formation of C---C and C---O bonds upon electron impact

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 organophosphorus compounds—XXXVI: Simple new routes to phosphorins from 2-hydroxy-, 2-mercapto-, and 2-aminobenzoic acids and their derivatives

2-Hydroxybenzoic acid heated with 2,4 - bis(4 - methoxyphenyl) - 1,3,2,4 - dithiadiphosphetane - 2,4 -disulfide, 1, gave 2 - (p - methoxyphenyl) - 4$\text{H}$ - 1,3,2 - benzoxathiaphosphorin - 4 - one 2 - sulfide, 3, and its thio-analogue, 4, while its ethyl or phenyl esters gave 4 as the sole product. 2 - Mercaptobenzoic acid and its ethyl ester when heated with 1 produced 3$\text{H}$ - 1,2 - benzodithiole - 3 - one, 8, 3$\text{H}$ -1,2 - benzodithiole - 3 - thione, 9, and 2- (p - methoxyphenyl) - 4$\text{H}$ - 1,3,2 - benzodithia - phosphorin - 4 - one 2 - sulfide, 10. The reaction of 2 -aminobenzoic acid with 1 gave 1,2 - dihydro - 2 - (p - methoxyphenyl) - 4$\text{H}$ - 3,1,2 - benzoxaphosphorin - 4 - one 2 - sulfide, 12. Reactions of 1 with methyl 2 - aminobenzoate and 2 - aminobenzamides are described. Mechanistic considerations for the formation of the heterocyclic phosphorus compounds are presented.     

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

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.     

Thiophene chemistry—IX Preparation and dealkylation of 5-substituted 2-t-butoxythiophenes

Different substituents have been introduced into the 5-position of 2-t-butoxythiophene and by subsequent acid-catalyst dealkylation the corresponding hydroxythiophenes (or their different tautomeric forms) have been isolated in high yields. By NMR, IR and UV-spectroscopy the constitution and the composition of the different tautomeres have been determined. The reaction between carbonyl compounds and 5-t-butoxy-2-thiophenelithium gives carbinols, which upon heating with p-toluenesulphonic acid yielded 5-methylene-3-thiolen-2-ones.     

2, 4-bis(4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane 2, 4-disulfide,lr, as a new activation reagent in preparation of peptides,amides and esters

Abstract

2, 4-Bis(4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane 2, 4-disulfide, LR, is easily prepared by refluxing P₄S₁₀ in anisole for two hours produces the title compound in high yield.     

Electron impact studies. CXXIV—Negative ion mass spectra of organic functional groups. Thioacetanilides

The thioacetanilide negative molecular ion (produced by secondary electron capture) is stable, but it fragments after collisional activation to yield [C₆H₅NH]^? by cleavage α to the C?S grouping. The negative molecular ions of (substituted) o-nitrothioacetanilides undergo a series of extremely complex rearrangement reactions. For example, the molecular anion derived from o-nitro-N-methylthioacetanilide yields both acetate and thioacetate anions as major fragment ions.     

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

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 (CH₂Cl₂) with β-diketones or their carbon disulphide adducts (1,3-di-thietanes).     

Enamine chemistry—XXIII: The [4+2] cycloaddition reactions between enaminothiones and electrophilic olefins and acetylenes

The enamino-thione, 1c, reacts with acrylonitrile and 2-chloroacrylonitrile at room temperature to give 3,4-dihydro-4-(1-pyrrolidinyl)-2$\text{H}$-thiopyrans, 4 and 5, respectively. The reaction between 1-aryl-3-(1-pyrrolidinyl) (piperidino)-apropene-1-thiones, 1a-c (1d-f), and dimethyl acetylenedicarboxylate gives 4-(1-pyrrolidiny)(piperidino)-4$\text{H}$-thiopyrans, 6a-c (6d-f). Compounds 1a-c (1d-f) and ethyl propiolate produce 2-(1-pyrrolidinyl) (piperidino)-2$\text{H}$-thiopyrans, 8a-c (8d-f), and a new type of rearrangement is observed. The 2$\text{D}$-thiopyran, 9, is formed from 1b and ethyl 3$\text{D}$-propiolate, which elucidates the mechanism. ¹H and ¹³C NMR data of 6 and 7 are discussed.     

5-phenyl-1,2,3,4-thiatriazole-3-oxide: A new class of heteroaromatic N-oxides

Oxidation of 5-phenyl-1,2,3,4-thiatriazole (1) with peroxytrifluoroacetic acid yields 5-phenyl-1,2,3,4-thiatriazole-3-oxide (2) a representative of a new class of heteroaromatic N-oxides. The structure is based on the mass spectral fragmentation of 2 and the isotope labelled with ¹⁵N at position 2. IR and ESCA measurements are consistent with this assignment. The thermal, photochemical, and chemical properties of the oxide are discussed.     

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

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.