Sulfanyl Radical Addition Research Articles

Sulfanyl radical promoted C4′–C5′ bond scission of 5′-oxo-3′,4′-didehydro-2′,3′-dideoxynucleosides

Treatment of C5'-aldehydes, under mildly basic conditions leads to the formation of 3',4'-didehydroaldehydes, and furfural. Sulfanyl radical addition eventually gives rise to the lactones, through C4'-C5' bond scission of the 1,2-dioxetane intermediates.

Radical cyclization in heterocycle synthesis. Part 14. A simple and effective preparation of cyclic oxime ethers by photochemical radical addition–cyclization of acyclic oxime ethers

The sulfanyl radical addition–cyclization of acyclic oxime ethers containing alkene groups proceeded smoothly under photochemical conditions to give the cyclic oxime ethers.

Radical Cyclization in Heterocycle Synthesis. Part 13. Sulfanyl Radical Addition—Cyclization of Oxime Ethers and Hydrazones Connected with Alkenes for Synthesis of Cyclic β‐Amino Acids.

Abstract A combination of sulfanyl radical addition–cyclization of the oxime ethers and hydrazones connected with alkenes and subsequent conversion of a phenylsulfanylmethyl group to a carboxyl group provides a novel method for the construction of the cyclic β-amino acids. Upon treatment with thiophenol in the presence of AIBN, the oxime ethers and hydrazones smoothly underwent sulfanyl radical addition-cyclization to give the 2-(phenylsulfanylmethyl)cycloalkylamine. This method was successfully applied to the practical synthesis of 2-aminocyclopentanecarboxylic acid and 4-amino-3-pyrrolidinecarboxylic acid.

Radical cyclization in heterocycle synthesis. Part 13: Sulfanyl radical addition–cyclization of oxime ethers and hydrazones connected with alkenes for synthesis of cyclic β-amino acids

A combination of sulfanyl radical addition–cyclization of the oxime ethers and hydrazones connected with alkenes and subsequent conversion of a phenylsulfanylmethyl group to a carboxyl group provides a novel method for the construction of the cyclic β-amino acids. Upon treatment with thiophenol in the presence of AIBN, the oxime ethers and hydrazones smoothly underwent sulfanyl radical addition-cyclization to give the 2-(phenylsulfanylmethyl)cycloalkylamine. This method was successfully applied to the practical synthesis of 2-aminocyclopentanecarboxylic acid and 4-amino-3-pyrrolidinecarboxylic acid.

ChemInform Abstract: Radical Cyclization in Heterocycle Synthesis. Part 12. Sulfanyl Radical Addition—Addition—Cyclization (SRAAC) of Unbranched Diynes and Its Application to the Synthesis of A‐Ring Fragment of 1α,25‐Dihydroxyvitamin D3.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sulfanyl radical addition–cyclization and its synthetic application

Abstract This review summarizes a new efficient carbon–carbon bond-forming reaction based on sulfanyl radical addition–cyclization, which proceeds by the formation of a carbon-centered radical species generated by the addition of a sulfanyl radical to a multiple bond and then intramolecular addition of the resulting carbon-centered radical to a multiple bond. The synthetic potentiality was demonstrated by the syntheses of anantine, oxo-parabenzlactone, cispentacin, vitamin D, and α-kainic acid.

Radical cyclization in heterocycle synthesis. 11.(1) A novel synthesis of alpha,beta-disubstituted gamma-lactones via sulfanyl radical addition-cyclization using hydroximates as a tether

A combination of sulfanyl radical addition-cyclization of dienes connected with hydroximates and subsequent conversion of the resulting cyclic hydroximate to the lactones provides a novel method for the construction of alpha,beta-disubstituted gamma-lactones. Upon treatment with thiophenol in the presence of AIBN, dienes connected with hydroximates smoothly underwent sulfanyl radical addition-cyclization to give cyclic cis- and trans-hydroximates. Hydrolysis of cyclic hydroximates gave the desired cis- and trans-lactones in high yield. This method was successfully applied to the practical synthesis of (+/-)-oxo-parabenzlactone.

Radical Cyclization in Heterocycle Synthesis. Part 10: A Concise Synthesis of (−)-Kainic Acid via Sulfanyl Radical Addition–Cyclization–Elimination Reaction

Sulfanyl radical addition–cyclization–elimination of diallylamines in the presence of thiophenol and AIBN gave the 2,3,4-trisubstituted pyrrolidine in high yield. This reaction was extended to a radical cyclization using a catalytic amount of thiophenol. A successful application was demonstrated by the asymmetric synthesis of (−)-kainic acid.

Thiol radical addition to alkynes. Sulfanyl radical addition and hydrogen atom abstraction relative reaction rates

2-(Toluenesulfanyl)- 1 and 2-(benzenesulfanyl)-phenylacetylene 10 reacted with benzenethiol and toluenethiol, respectively, in the presence of AIBN at 84 and 154 °C to give products deriving from vinyl radicals 2 which undergo hydrogen abstraction reaction and 5- ortho and 5- exo cyclization onto both the adjacent phenyl rings in competition with the β-fragmentation. Definitive evidence has been obtained that alkanesulfanyl radical addition to the alkyne triple bond is a non-reversible process, whereas arenesulfanyl radicals add in a reversible mode. Competing experiments involving several alkynes towards benzenethiol and benzeneethanethiol radical addition have been performed in order to determine the relative rate constants of the sulfanyl radical addition to the alkyne triple bond (k 1) and the hydrogen abstraction reaction by the resulting vinyl radicals (k H). The k 1 values are mainly determined by the vinyl radical stabilization provided by the C-(α) vinyl radical substituent, whereas the k H values seem to be mainly determined by polarity factors. An unexpected different behavior between α-propyl and α-long-chain substituents is discussed in terms of different hybridization of the vinyl radical.

ChemInform Abstract: Rearrangements and Cyclizations in Vinyl Radicals Promoted by Sulfanyl Radical Addition to Alkynes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Sulfanyl Radical Addition to Alkynyl Azides: An Insight into Vinyl Radical Cyclization onto the Azido Function.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Stereoselective Cyclizations and Rearrangements in Vinyl Radicals Promoted by Regioselective Sulfanyl Radical Addition to Enynes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sulfanyl radical addition to alkynyl azides: an insight into vinyl radical cyclization onto the azido function

5- Exo-Cyclization of 2-sulfanylvinyl radicals 16 and 21 is a fast process which prevents intramolecular addition to the sulfanyl aromatic ring and hydrogen abstraction. In contrast, the 2-sulfanylvinyl radicals 3 and 9 are reluctant to add to their aliphatic azido substituent either in a π-( endo) or in a π-( exo) mode. These radicals exclusively undergo cyclization onto the adjacent aromatic ring and H-transfer from the thiol present.

Stereoselective Cyclizations and Rearrangements in Vinyl Radicals Promoted by Regioselective Sulfanyl Radical Addition to Enynes

Regioselective radical addition of 4-cyanotoluenethiol (1a) to enynes 3−6 leads to vinyl radicals 7−10 that can undergo five- or six-membered cyclization onto styrene or terminal double bonds in competition with 5-exo cyclization onto the aryl ring. The latter affords spiro-cyclohexadienyl radical intermediates which can either be trapped by 2-cyanoisopropyl radicals or give 1,4-aryl migration products. Regioselective radical addition of phenethanethiol (1b) to enynes 3−6 gives radicals 11−14 which undergo five- or six-membered cyclization onto the alkene double bond; the stereoelectronically disfavored 6-exo cyclization can compete with intermolecular hydrogen abstraction and (to a small extent) with 1,5-hydrogen migration. The 5- and 6-(π-exo)exo cyclization of vinyl radicals 7, 9, 11−13 is highly stereoselective and exclusively or predominately affords products deriving from the (Z)-isomers. Stereochemical evidence indicates that the six-membered endo-cyclization products 30 and 50 could derive from a ...

Generation of Iminyl Radicals through Sulfanyl Radical Addition to Vinyl Azides

Benzenethiol and 2-benzo[b]thiophenethiol undergo almost instantaneous reaction with α-azidostyrene and 1-azido-trans-stilbene in benzene, at room temperature, to give corresponding β-sulfanylated imines and enamines in virtually quantitative yield. With α-azidostyrene, phenethyl and allyl mercaptan are found to react in a similar fashion, but to rates very much lower. Results are interpreted in terms of radical-chain reactions involving intermediacy of 2-sulfanyliminyl radicals which could result from sulfanyl radical attack at the azide β-carbon followed by nitrogen extrusion by the ensuing radical adduct.

Radical cyclisation in heterocycle synthesis. Part 1. Sulfanyl radical addition–cyclisation of dienylamides for lactam synthesis

A new method for the synthesis of five- to eight-membered lactams by sulfanyl radical mediated addition–cyclisation of dienylamides is described. The sulfanyl radical addition–cyclisation of the dienylamide 1 was systematically investigated under four different conditions and was found to give the cyclised lactams 2–6 in 54–79% yield. The stereo- and regio-selectivity of sulfanyl radical addition–cyclisation was established from the preferential formation of the trans-cyclised lactam 3 and also from the substituent effects in the Cyclisation of the dienylamides 11–18. The sulfanyl radical mediated addition–cyclisation was successfully applied to the construction of the six- and eight-membered lactams 28a, b.