Enantioselective Radical Addition/Cross‐Coupling of Organozinc Reagents, Alkyl Iodides, and Alkenyl Boron Reagents

Abstract

Ah ybrid transition-metal/radical process is described that results in the addition of organozinc reagents and alkylh alides across alkenyl boron reagents in an enantioselective catalytic fashion. The reaction can be accomplished both intermolecularly and intramolecularly,p roviding useful product yields and high enantioselectivities in both manifolds.

Nickel‐CatalyzedDicarbofunctionalization of Alkenes†

“…In 2019, the Morken group successfully employed tertiary alkyl iodides in the nickel‐catalyzed asymmetric dicarbofunctionalization of boryl ethenes with organic zinc reagents (Scheme 31a). [ 85 ] In their previous work, [ 86 ] a radical/polar crossover pathway [ 87‐89 ] initiated by Ni complexes led to racemic products (Scheme 31b). To avoid the single electron oxidation step of anionic α‐boryl radical, alkene tethered with a neutral boron was used, which enabled the formation of a stable α‐boryl radical upon radical addition (Scheme 31c).…”

Photoredox‐Mediated Reaction of gem‐Diborylalkenes: Reactivity Toward Diverse 1,1‐Bisborylalkanes

“…We posit that one efficient way to form gem ‐diboryl radical ( II ) can be achieved by adding carbon‐centered radicals to gem ‐diborylalkenes 2 as described in Scheme F. An analogous alkylation via generating α‐monoboryl carbon‐centered radicals IV using vinyl‐boron species III by adding a variety of carbon‐centered radicals to vinyl‐borons III has been reported by Aggarwal, Zard, Morken, Studer, Shi, Molander, and others (See Scheme E) . Considering the fact that gem ‐diboryalkenes ( 2 ) are more electron deficient than vinyl‐borons III are, they ( 2 ) are expected to be suitable candidates for this type of radical addition scenario.…”

Recent developments in nickel-catalyzed intermolecular dicarbofunctionalization of alkenes

“…4A). 15 Taking advantage of the stability of the a-boryl radical, 16 alkyl zinc halides and tertiary alkyl halides are effective coupling partners using 10 mol% NiBr 2 $glyme and 13 mol% chiral diamine ligand L3. Interestingly, the use of pinacol as boron protecting group was necessary to achieve high ee.…”