Rita Fochi

2-Deuterio-1,3-benzodithiolium perchlorate: A useful synthon for the preparation of aldehydes-1-d

Abstract 2-Deuterio-1,3-benzodithiolium perchlorate reacted with Grignard reagents to give 2-alkyl or 2-aryl-2-deuterio-1,3-benzodithioles, which in turn could be hydrolysed to corresponding aldehydes-1-d.

Deracemization of thiol esters of α-arylpropionic acids

Abstract Racemic thiol esters of α-arylpropionic acids were deracemized by a procedure which featured deprotonation with LDA or KHMDS, transformation into the TMS or TBDMS enol ethers, and enantioselective protonation of the silyl enol ethers using ( R )-1,1′-bi-2-naphthol/SnCl 4 . Oxidative hydrolysis of the enantiomerically enriched mixtures of thiol esters thus obtained yielded the ( S )-enantiomers of ibuprofen and naproxen with ees up to 82%.

Convenient procedure for converting 1,3-dithiolane-2-thiones into 1,3-dithiolan-2-ones

1,3-Dithiolan-2-ones have been obtained by reaction of 1,3-dithiolane-2-thiones and epoxides in the presence of HBF4·Et2O. The reactions, carried out in anhydrous CH2CL2 at 0–5 °C→room temperature (Procedure A) or in anhydrous chlorobenzene at 0–5-→80 °C (Procedure B), gave product yields of 63–95%. By Procedure B it was also possible to isolate the intermediates 1-oxa-4,6,9-trithiaspiro[4.4]nonanes in good yields (66–85%). Reaction pathways are proposed.

General methods for synthesizing 2,4-diacylpyrroles and their precursors containing one or two masked acyl groups

A thorough study of the synthesis of 2,4-diacylpyrroles by direct acylation of pyrrole and 2- and 3-acylpyrroles is reported. Among these, Friedel–Crafts acylation of 3-acylpyrroles is the most general and advantageous method because it utilises easily accessible starting materials. In addition it is always regiospecific and readily provides 2,4-diacylpyrroles containing identical or different acyl groups in very high yields (81–100%) under mild conditions. Alternative procedures concern the synthesis of precursors of 2,4-diacylpyrroles containing one or two acyl groups masked by a 1,3-benzodithiolyl or 1,3-benzoxathiolyl group and subsequent hydrolysis with HgO–35% aq. HBF4Me2SO. Overall yields are always good (52–60%). Indirect acylation constitutes a secure complement to direct acylation when it is necessary to operate in the presence of protected acyl groups.

Synthesis of 5-Hydroxy-1, 3-Benzoxathiole

Abstract 5-Hydroxy-1,3-benzoxathiole (4) is the key intermediate for the preparation of several 1,3-benzoxathiole derivatives - e.g. acetals, ethers, sulfonates, esthers, etc. - which have shown interesting biological activities as juvenoids, insecticides and / or synergists for natural and synthetic insecticides1.

Pentatomic heteroaromatic cations. Part 10. A new route for the reduction of the functional group of carboxylic acids, acid chlorides, anhydrides, esters, nitriles, trihalogenomethyl compounds, aldehydes, and ketones to methyl or methylene groups

The reactions of carboxylic acids, acid chlorides, anhydrides, esters, nitriles, and trichloromethyl and trifluoromethyl derivatives with benzene-1,2-dithiol in tetrafluoroboric acid–ether or boron trifluoride–ether, generally affords excellent yields of 2-substituted 1,3-benzodithiolylium tetrafluoroborates. These can be easily reduced with sodium borohydride to 2-substituted 1,3-benzodithioles, which by scission of the C(2)–S bond with sodium in liquid ammonia give the corresponding hydrocarbons. Also the carbonyl group of aldehydes and ketones can be reduced to the methylene group by related reactions.

Pentatomic heteroaromatic cations. Part VI. New syntheses of aldehydes and ketones by reaction of 1,3-benzodithiolylium salts with Grignard reagents

2-Substituted and 2,2-disubstituted 1,3-benzodithioles are formed when 1,3-benzodithiolylium and 2-phenyl-1,3-benzodithiolylium perchlorates, respectively, react with Grignard reagents. The products can be hydrolysed to aldehydes and ketones by treatment with chloramine τ followed by mercury(II) chloride. This procedure offers a sound alternative method for the synthesis of aldehydes by formylation of Grignard reagents, and it suggests a new route for the total synthesis of symmetric and asymmetric ketones from alkyl and aryl halides via such reagents.

A General Procedure to Selectively Prepare N-Alkylanilines by an Unexpected Reaction of (Z)-(tert-Butylsulfanyl)(aryl)diazenes with Alkyllithium Reagents

A general procedure has been set up to prepare, selectively, the N-monoalkylanilines 7, reacting (Z)-(tert-butylsulfanyl)(aryl)diazenes 3 with alkyllithium 6 (MeLi, BuLi, s-BuLi, n-C 6 H 1 3 Li). The reactions were carried out in anhydrous diethyl ether at 0 °C or -78 °C, depending on the reagent 6, and then at room temperature. In optimal conditions the yields of the pure products 7 (uncontaminated by dialkylation products) were from good to excellent: for 38 considered examples, 34 were positive with yields varying between 61% and 91% (average yield 78%). Collateral proofs were carried out to support a hypothesized reaction mechanism.

CONVENIENT ROUTE FOR THE SYNTHESIS OF 3-SUBSTITUTED AND 3,4-DISUBSTITUTED PYRROLE-2,5-DICARBALDEHYDES

3-Substituted and 3,4-disubstituted pyrrole-2,5-dicarbaldehydes have been obtained by hydrolysis with HgO–35% aq. HBF4–DMSO of the intermediates 4 and 5 prepared by electrophilic substitution reactions on 2,5-bis(1,3-benzodithiol-2-yl)pyrrole. The overall yields starting from pyrrole ranged from 41–88%.

Synthetic application of lithiated tris(methylthio)methane: preparation of aliphatic methyl thiolcarboxylates from the corresponding halides. Convenient synthesis of tris(methylthio)methane

A thorough study directed towards the synthesis of methyl thiolcarboxylates was made on the basis of the following steps: (i) conversion of alkyl halides into the corresponding trimethyl trithioorthocarboxylates by using tris(methylthio)methyllithium in THF at –78 °C; (ii) selective hydrolysis of the intermediates to methyl thiolcarboxylates by using 35% aq. HBF4 in DMSO or, in some cases, in THF. The overall yields of the two stages are, usually, between 70 and 88%. By this procedure it is also possible to incorporate 8O in the carbonyl group of thiol esters (∼98% isotopic purity). Furthermore, a new, convenient method for the preparation of tris(methylthio)methane as the precursor of tris(methylthio)methyllithium was developed.