Direct Construction of Quaternary Carbons from Tertiary Alcohols via Photoredox-Catalyzed Fragmentation of<i>tert</i>-Alkyl<i>N</i>-Phthalimidoyl Oxalates

Lackner, Gregory L.; Quasdorf, Kyle W.; Overman, Larry E.

doi:10.1021/ja408971t

Cited by 277 publications

(143 citation statements)

References 27 publications

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“…Following on from their earlier work on N-(acyloxy)phthalimides (see Scheme 2), Overman and co-workers developed a method to exploit tertiary alcohols as radical precursors through the intermediacy of N-phthalimidoyl oxalates 55. [81] Through the use of a similar catalytic system, a range of tertiary alcohol derivatives could be efficiently coupled with various Michael acceptors under mild conditions (Scheme 34). A similar mechanism was proposed, based on the reductive quenching of the Ru II * catalyst followed by reductive SET substrate activation, radical addition, and H-abstraction.…”

Section: C(sp 3 )-Alcohol Derivativesmentioning

confidence: 99%

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp³)‐Substrates

Roslin

Odell

2017

Eur J Org Chem

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Over the past decade, visible-light photocatalysis has emerged as one of the brightest and most dynamic fields in modern organic chemistry. By employing a transition-metal-or organic-dye-based photocatalyst in conjunction with a low-energy visible-light source, this synthetic manifold allows the facile generation of radical intermediates that can subsequently be directed through a wide range of transformations. Although

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Section: C(sp 3 )-Alcohol Derivativesmentioning

confidence: 99%

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp³)‐Substrates

Roslin

Odell

2017

Eur J Org Chem

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“…In this article, we provided details of our modification of the Okada method, and a broader survey of the notable utility of this visible-light photocatalytic method for C–C bond formation and the construction of quaternary carbon centers. In particular, we examine a selection of coupling reactions to allow a direct comparison of ( N -acyloxy)phthalimides and N -phthalimidoyl oxalates 5,6 as precursors of tertiary carbon radicals for C–C bond-forming reductive coupling and allylic and vinylic substitution reactions. We also report investigations that identify both hydrogen-atom transfer and single-electron reduction followed by protonation as viable termination steps of these C–C bond-forming coupling reactions.…”

Section: Introductionmentioning

confidence: 99%

Constructing Quaternary Carbons from N-(Acyloxy)phthalimide Precursors of Tertiary Radicals Using Visible-Light Photocatalysis

2015

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Tertiary carbon radicals have notable utility for uniting complex carbon fragments with concomitant formation of new quaternary carbons. This article explores the scope, limitations and certain mechanistic aspects of Okada’s method for forming tertiary carbon radicals from (N-acyloxy)phthalimides by visible-light photocatalysis. Optimized conditions for generating tertiary radicals from (N-acyloxy)phthalimide derivatives of tertiary carboxylic acids by visible-light irradiation in the presence of 1 mol% of commercially available Ru(bpy)3(PF6)2, diethyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate (8) and i-Pr2NEt, and their coupling in dichloromethane at room temperature with alkene acceptors were developed. Four representative tertiary (N-acyloxy)phthalimides and 15 alkene radical acceptors were examined. Both reductive couplings with electron-deficient alkenes and radical substitution reactions with allylic and vinylic bromides and chlorides were examined with many such reactions occurring in good yield using only a slight excess (typically 1.5 equiv) of the alkene. In general, the yields of these photocatalytic reactions were higher than the analogous transformations of the corresponding N-phthalimidoyl oxalates. Deuterium labeling and competition experiments reveal that the reductive radical coupling of tertiary (N-acyloxy)phthalimides with electron-deficient alkenes can be terminated by both hydrogen-atom transfer and single-electron reduction followed by protonation, and that this mechanistic duality is controlled by the presence or absence of i-Pr2NEt.

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“…After some experimentation, a general route to access the requisite N-hydroxyphthalimido oxamide radical precursors on gram-scale was developed, via the acylation of anilines with chloro N-phthalimidoyl oxalate, readily prepared by Overman's method, 30 followed by successive aqueous washings with dilute aq. HCl and then saturated aq.…”

Section: Resultsmentioning

confidence: 99%

Photoredox-catalyzed procedure for carbamoyl radical generation: 3,4-dihydroquinolin-2-one and quinolin-2-one synthesis

2017

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Direct Construction of Quaternary Carbons from Tertiary Alcohols via Photoredox-Catalyzed Fragmentation oftert-AlkylN-Phthalimidoyl Oxalates

Abstract: A convenient method for the direct construction of quaternary carbons from tertiary alcohols by visible-light photoredox coupling of tert-alkyl N-phthalimidoyl oxalate intermediates with electron- deficient alkenes is reported.

Cited by 277 publications

References 27 publications

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp³)‐Substrates

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp³)‐Substrates

Constructing Quaternary Carbons from N-(Acyloxy)phthalimide Precursors of Tertiary Radicals Using Visible-Light Photocatalysis

Photoredox-catalyzed procedure for carbamoyl radical generation: 3,4-dihydroquinolin-2-one and quinolin-2-one synthesis

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Direct Construction of Quaternary Carbons from Tertiary Alcohols via Photoredox-Catalyzed Fragmentation oftert-AlkylN-Phthalimidoyl Oxalates

Abstract: A convenient method for the direct construction of quaternary carbons from tertiary alcohols by visible-light photoredox coupling of tert-alkyl N-phthalimidoyl oxalate intermediates with electron- deficient alkenes is reported.

Cited by 277 publications

References 27 publications

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp3)‐Substrates

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp3)‐Substrates

Constructing Quaternary Carbons from N-(Acyloxy)phthalimide Precursors of Tertiary Radicals Using Visible-Light Photocatalysis

Photoredox-catalyzed procedure for carbamoyl radical generation: 3,4-dihydroquinolin-2-one and quinolin-2-one synthesis

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Product

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Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp³)‐Substrates

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp³)‐Substrates