Radical Translocation Reactions Research Articles

Short I⋯O Interactions in the Crystal Structures of Two 2-Iodo-Phenyl Methyl-Amides as Substrates for Radical Translocation Reactions

Radical translocation reactions are finding various uses in organic synthesis, in particular the stereospecific formation of complex natural products. In this work, the syntheses and single-crystal structures of two substituted 2-iodo-phenyl methyl-amides are reported, namely cyclo-propane carboxylic acid (2-iodo-phenyl)-methyl-amide, C11H12INO (1), and cyclo-heptane carboxylic acid (2-iodo-phenyl)-methyl-amide, C15H20INO (2). In each case, the methyl-amide group has a syn conformation, and this grouping is perpendicular to the plane of the benzene ring: these solid-state conformations appear to be well setup to allow an intramolecular hydrogen atom transfer to take place as part of a radical translocation reaction. Short intermolecular I⋯O halogen bonds occur in each crystal structure, leading to [010] chains in 1 [I⋯O = 3.012 (2) Å] and isolated dimers in 2 [I⋯O = 3.024 (4) and 3.057 (4) Å]. The intermolecular interactions are further quantified by Hirshfeld surface analyses.

Radical cyclizations of cyclic ene sulfonamides occur with β-elimination of sulfonyl radicals to form polycyclic imines.

Radical cyclizations of cyclic ene sulfonamides provide stable bicyclic and tricyclic aldimines and ketimines in good yields. Depending on the structure of the precursor, the cyclizations occur to provide fused and spirocyclic imines with five-, six-, and seven-membered rings. The initial radical cyclization produces an α-sulfonamidoyl radical that undergoes elimination to form the imine and a phenylsulfonyl radical. In a related method, 3,4-dihydroquinolines can also be produced by radical translocation reactions of N-(2-iodophenylsulfonyl)tetrahydroiso-quinolines. In either case, very stable sulfonamides are cleaved to form imines (rather than amines) under mild reductive conditions.

Radical translocation reactions in synthesis

This review highlights synthetically useful transformations of organic free-radicals in which a key step is relocation of the radical site by intramolecular abstraction either of a hydrogen atom or a group (e.g. phenyl, cyano, trialkylsilyl). The material is organised around the nature of the radical that initiates translocation and coverage is largely confined to reports that have appeared within the past decade, reference to earlier work only being made in order to establish a context for more recent results.

Synthesis of bridged azabicyclic compounds using radical translocation reactions of 1-(o-bromobenzoyl)-2-(prop-2-enyl)pyrrolidines

A new synthesis of the 7-azabicyclo[2.2.1]heptane and 8-azabicyclo[3.2.1]octane systems is described in which α-acylamino radicals generated from l-(o-bromobenzoyl)-2-(prop-2-enyl)pyrrolidines by a Bu3SnH-mediated radical translocation reaction are cyclised. Treatment of methyl l-(o-bromobenzoyl)-2-(prop-2-enyl)pyrrolidine-2-carboxylate 3a with Bu3SnH in the presence of a catalytic amount of azoisobutyronitrile in boiling toluene gave the 7-azabicyclo[2.2.1]heptane 4a(a 5-exo cyclisation product)[42% yield as a diastereoisomeric mixture (66 : 34)] and the 8-azabicyclo[3.2.1]octane 5a(a 6-endo product)(30%), together with the reduction product 6a(12%). The regiochemistry (5-exo/6-endo) of this cyclisation could be controlled by the introduction of a substituent on the prop-2-enyl group. The substituent(s) at the 2- and/or 4-position(s) of the pyrrolidine ring were found to play an important role in this cyclisation.

Amide-based protecting/radical translocating (PRT) groups. Generation of radicals adjacent to carbonyls by 1,5-hydrogen transfer reactions of o-iodoanilides

The o-iodoanilide group is shown to be broadly useful for the generation and subsequent reactions of radicals adjacent to carboxyl groups. The results indicate that this group is one of the best “protecting/radical translocating” (PRT) groups introduced to date. Beyond its good performance in radical translocation reactions, it is easy to introduce, serves as a reasonable protecting group both before and after the translocation, and (with appropriate modifications) is easy to remove.

Radical translocation reactions across amides. 1,5-Hydrogen-transfer reactions of o-iodobenzamides and N-(o-iodobenzyl) amides

Radicals derived from N,N-disubstituted o-iodobenzamides undergo rapid 1,5-hydrogen-transfer reactions. The regioselectivity of these reactions is coupled to the rotamer population of the starting iodobenzamide, and the products vary with changing amide substituents. Related 1,5-hydrogen-transfer reactions are observed for N-alkyl-N-(o-iodobenzyl)-benzamides and -acetamides.

ChemInform Abstract: Radical Translocation Reactions of Vinyl Radicals: Substituent Effects on 1,5‐Hydrogen‐Transfer Reactions.

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.

Radical translocation reactions of vinyl radicals: substituent effects on 1,5-hydrogen-transfer reactions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRadical translocation reactions of vinyl radicals: substituent effects on 1,5-hydrogen-transfer reactionsDennis P. Curran and Wang ShenCite this: J. Am. Chem. Soc. 1993, 115, 14, 6051–6059Publication Date (Print):July 1, 1993Publication History Published online1 May 2002Published inissue 1 July 1993https://doi.org/10.1021/ja00067a021RIGHTS & PERMISSIONSArticle Views1912Altmetric-Citations160LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (3)»Supporting Information Supporting Information Get e-Alerts

1,2-Asymmetric induction in radical reactions. Deuteration and allylation reactions of β-oxy- o-Iodoanilides.

Chiral radicals were generated by radical translocation reactions of β-oxy-o-iodoanilides and their asymmetric deuteration and allylation reactions were studied.

Competing radical translocation reactions of tertiary N-(2-bromobenzyl)- and N-(8-bromonaphthyl)-acetamides

The radical translocation reactions in N,N-disubstituted acetamides 10a, 14a–d and trifluoroacetamides 10b, 14e–f have been studied by deuteration experiments with n-Bu 3SnD. The intramolecular hydrogen atom transfer from the N-alkyl side chain to the aryl radical takes place through competing 6-, 7-, 8-membered ring transition states.

ChemInform Abstract: Radical Translocation Reactions of o‐Iodoanilides: The Use of Carbon‐ Hydrogen Bonds as Precursors of Radicals Adjacent to Carbonyl Groups.

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.

Iodine atom transfer addition reactions with alkynes. Part 2; α-iodocarbonyls

1°-Iodo esters, ketones, and nitriles react smoothly in atom transfer addition reactions with alkyl- substituted (nucleophilic) alkynes, but a 3°-iodoester prefers to add to ester-substituted (electrophilic) alkynes. These atom transfer additions are suited for preparing precursors for radical translocation reactions as well for appending β- lactam side chains.

Radical translocation reactions of o-iodoanilides: the use of carbon-hydrogen bonds as precursors of radicals adjacent to carbonyl groups

Radical translocation reactions of o-iodoanilides: the use of carbon-hydrogen bonds as precursors of radicals adjacent to carbonyl groups