Sulfanyl Radical Addition-cyclization Research Articles

Radical Cyclization in Heterocycle Synthesis 15. Relationship between a Radical Species and Radical Acceptors of Three Different Types of Double Bond in Radical Addition-Cyclization

Relationship between a radical species and radical acceptors of three different types of double bond in radical addition-cyclization was systematically investigated. Substrates carrying alpha,beta-unsaturated amide, isolated olefin, and oxime ether moieties underwent radical addition-cyclization to give differently substituted lactams depending upon the radicals used. The sulfanyl radical addition-cyclization of the substrate proceeded smoothly to give the 5-membered lactam having an alkoxyamino group as a result of preferable addition of an intermediary alpha-carbonyl radical to the oxime ether. On the other hand, the triethylborane-mediated radical addition-cyclization gave the lactam bearing an iodomethyl group as a result of addition to an intermediary alpha-carbonyl radical to isolated olefin. The different regioselectivity was explained by the stability of the intermediary radical and the interaction between SOMO and HOMO.

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.

Heterocycle Synthesis via Radical Addition-Cyclization of Oxime Ethers.

Oxime ethers connected by a tether to aldehydes or ketones efficiently cyclized via stannyl radical addition-cyclization to give a new entry to heterocyclic amino alcohols. The SmI2-induced radical cyclization was found to be effective for preparing cyclic trans-amino alcohols. These radical reactions provide a novel method for the synthesis of (-) -balanol, aminocyclitols, 1-deoxynojirimycin, 2-substituted 5-amino-4-piperidinol, and nucleoside analogs. The sulfanyl radical addition-cyclization-elimination reaction was developed, which was successfully applied to the synthesis of (-) -kainic acid. The sulfanyl radical addition-cyclization of oxime ethers gave a method for synthesis of rigidified cyclic β-amino acids. The carbon radical addition-cyclization reaction of substrates having two different radical acceptors such as acrylate and aldoxime ether moieties proceeded even in aqueous media via a diastereoselective tandem C-C bond-forming process, providing a method for asymmetric synthesis of γ-butyrolactones and γ-amino acids.

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.

A Concise Synthesis of Rigidified β-Amino Acids via Sulfanyl Radical Addition-Cyclization of Oxime Ethers and Hydrazones

A Concise Synthesis of Rigidified β-Amino Acids via Sulfanyl Radical Addition-Cyclization of Oxime Ethers and Hydrazones

Radical cyclization in heterocycle synthesis. II. Total synthesis of (+/-)-anantine and (+/-)-isoanantine.

(±)-Anantine, (±)-isoanatine and related compounds were synthesized via two key reactions, sulfanyl radical addition-cyclization and stereoselective construction of the E-benzylidene moiety.

A Formal Synthesis of (+)-a-Allokainic Acid via Sulfanyl Radical Addition-Cyclization Reaction

A Formal Synthesis of (+)-a-Allokainic Acid via Sulfanyl Radical Addition-Cyclization Reaction