Regioselective radical hydroboration of electron-deficient alkenes: synthesis of α-boryl functionalized molecules

Huang, Yun‐Shuai; Wang, Jie; Zheng, Wan-Xin; Zhang, Feng‐Lian; Yu, You‐Jie; Zheng, Min; Zhou, Xiaoguo; Wang, Yifeng

doi:10.1039/c9cc06506g

Cited by 45 publications

(24 citation statements)

References 41 publications

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“…In contrast, complex 25 proved chemoselective in hydroboration of benzonitriles in the presence of additives bearing ester, alkene and isonitrile functionalities (Scheme B). Selective addition of HBPin to the cyano group was also observed for cyclohexene‐1‐carbonitrile (Scheme A) . However, as expected due to much less energy barriers for addition of HBPin to aldehydes and ketones, hydroboration of the substrates having formyl and acetyl functionalities was found to be non‐selective.…”

Section: Main Group Metal Catalystssupporting

confidence: 53%

“…Selective addition of HBPin to the cyano group was also observed for cyclohexene-1carbonitrile (Scheme 23A). [58] However, as expected due to much less energy barriers for addition of HBPin to aldehydes and ketones, hydroboration of the substrates having formyl and acetyl functionalities was found to be non-selective. Analogously, hydroboration of phenyl acetylenes was found to be preferable over benzonitriles.…”

Section: Main Group Metal Catalystsmentioning

confidence: 65%

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Catalytic Nitrile Hydroboration: A Route to N,N‐Diborylamines and Uses Thereof

Hayrapetyan

Khalimon

2020

Chemistry An Asian Journal

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Catalytic reduction of nitriles is considered as an attractive and atom‐economical route to a diversity of synthetically valuable primary amines. Compared to other methods, dihydroboration approach has been developed relatively recently but has already attracted the attention of many research groups due to reasonably mild reaction conditions, selectivity control and the access to N,N‐diborylamines, which emerged as powerful reagents for C−N bond forming reactions. Early developments in catalytic dihydroboration of nitriles implied precious metal catalysts along with harsh conditions and prolonged reaction times, whereas recent advances mostly rely on base and main group metal catalytic systems with significantly improved profiles. This minireview aims to provide an overview of advances and challenges of dihydroboration of nitriles with d‐, f‐ and main group metal catalysts. Mechanistic features of different catalytic systems, functional group tolerance and scope of the methods are also presented. The synthetic utility of N,N‐diborylamies, beyond simple protodeborylation, is discussed in the aspect of N‐arylation, imine and amide synthesis.

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Section: Main Group Metal Catalystssupporting

confidence: 53%

Section: Main Group Metal Catalystsmentioning

confidence: 65%

Catalytic Nitrile Hydroboration: A Route to N,N‐Diborylamines and Uses Thereof

Hayrapetyan

Khalimon

2020

Chemistry An Asian Journal

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“…The present photocatalytic approach provides a new solution for achieving radical arylborations of alkenes with exclusive regio‐ and diastereoselectivity control . The NHC‐boryl radical selectively added to the α‐carbon of electron‐deficient alkenes, while the aryl component was attached to the β‐carbon. The anti ‐stereochemistry was confirmed by X‐ray crystallographic analysis of compound 6 e .…”

Section: Resultsmentioning

confidence: 99%

New Radical Borylation Pathways for Organoboron Synthesis Enabled by Photoredox Catalysis

et al. 2020

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Radical borylation using N‐heterocyclic carbene (NHC)‐BH3 complexes as boryl radical precursors has emerged as an important synthetic tool for organoboron assembly. However, the majority of reported methods are limited to reaction modes involving carbo‐ and/or hydroboration of specific alkenes and alkynes. Moreover, the generation of NHC‐boryl radicals relies principally on hydrogen atom abstraction with the aid of radical initiators. A distinct radical generation method is reported, as well as the reaction pathways of NHC‐boryl radicals enabled by photoredox catalysis. NHC‐boryl radicals are generated via a single‐electron oxidation and subsequently undergo cross‐coupling with the in‐situ‐generated radical anions to yield gem‐difluoroallylboronates. A photoredox‐catalyzed radical arylboration reaction of alkenes was achieved using cyanoarenes as arylating components from which elaborated organoborons were accessed. Mechanistic studies verified the oxidative formation of NHC‐boryl radicals through a single‐electron‐transfer pathway.

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“…Meanwhile, computational studies by Rablen and Zipse revealed that the BDEs of B−H bonds in amine‐ and phosphine‐BH 3 complexes were generally reduced to 94–104 kcal/mol [3a,e] . In addition, NHC‐boryl radicals, pioneered by Fensterbank, Lacôte, Malacria, Curran, [5a] were demonstrated to exhibit diverse reactivity in many valuable transformations, including reductions of xanthates, [5b] alkyl/aryl halides, [5c–e] ketones, [5f] and cyanides, [5g] addition, [5h,6a–c] and tandem cyclizations [6d–e] . Recently, Curran, Taniguchi and Wang realized challenging radical addition trans ‐hydroboration of alkynes with NHC−BH 3 in access to NHC ( E )‐alkenylboranes [7] .…”

Section: Methodsmentioning

confidence: 99%

Boryl Radical‐Mediated C−H Activation of Inactivated Alkanes for the Synthesis of Internal Alkynes

et al. 2020

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An intriguing pyridine‐boryl radical‐mediated C−H alkynylation reaction of inactivated alkanes was described. The reaction features mild operation condition and wide substrate scope, and affords the corresponding products in moderate to good yields. Notably, The presence of 4‐cyanopyride N‐oxide was key to the success of the reaction. Cyclohexane are more easily to be functionalized in this reaction than toluene, which could be rationally explained by polarity‐match principle.

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Regioselective radical hydroboration of electron-deficient alkenes: synthesis of α-boryl functionalized molecules

Abstract: A radical hydroboration of electron-deficient alkenes was developed for the direct synthesis of diverse α-boryl functionalized molecules.

Cited by 45 publications

References 41 publications

Catalytic Nitrile Hydroboration: A Route to N,N‐Diborylamines and Uses Thereof

Catalytic Nitrile Hydroboration: A Route to N,N‐Diborylamines and Uses Thereof

New Radical Borylation Pathways for Organoboron Synthesis Enabled by Photoredox Catalysis

Boryl Radical‐Mediated C−H Activation of Inactivated Alkanes for the Synthesis of Internal Alkynes

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