Nucleophilic addition reactions of hindered unsaturated boranes. New synthesis of organoboranes

Transition metal and radical free 1,2-dicarbofunctionalisation of 1,1-arylboryl alkenes through dual C(sp3)-C(sp3) bond formation

“…A particular precedent on boron-activated nucleophilic addition to olefins by steric suppression of boron "ate" complex was reported for α-trimetylsilyl substituted vinyldimesitylboranes, although attempts to alkylate the alkeneborata intermediate were only successful with MeI. 24 Our hypothesis for the alkylation of alkeneborata intermediate 3, via SN2 nucleophilic substitution, gains strength since it occurs with aliphatic C(sp 3 ) halides (including allyl halides) but it does not react with aryl or vinyl halides, or tertiary alkyl iodides. The quantification of the nucleophilic character of α-boryl carbanions towards organic electrophiles, was previously predicted through theoretical calculations for the SN2 nucleophilic substitution reaction between bromoethane and alkeneborata carbanions, containing mesitylboranes or piancolboranes, demonstrating that the free-energy barriers (∆G ‡ SN2) are significantly lower when pinacolboryl motifs are involved.…”

Geminal Difunctionalization of Alkenylidene-Type Carbenoids by Using Interelement Compounds

“…Herein we report that bis(pinacolato)diboron ( 1 )5 and (dimethylphenylsilyl)(pinacolato)borane ( 2 )6 react with 1‐halo‐1‐lithioalkenes 4 ,7 alkylidene‐type carbenoids available from 1,1‐dihaloalkenes or 1‐haloalkenes 3 , to afford 1,1‐diborylalkenes 5 8 or 1‐boryl‐1‐silylalkenes 6 ,9 respectively. These products are readily converted into tri‐ or tetra‐substituted alkenes through various transition metal catalyzed carbon−carbon bond formations (Scheme ).…”

Geminal Difunctionalization of Alkenylidene-Type Carbenoids by Using Interelement Compounds

“…[8] Besides their role as structuredirecting agents, the A m ions can also introduce physical properties of interest to the magnetic system, leading to multiproperty materials. Along this line, we have synthesized a family of 2D compounds where the ªinnocentº quaternary onium cation has been replaced by redox-active species of the decamethylmetallocenium type [9] or organic donors such as BEDT-TTF (2,2'-bis (5,6-dihydro-1,3-dithiolo[4,5-b][1,4]di-…”

“…The addition of a reagent with a BÀB, SiÀB, or SiÀSi bond to unsaturated carbonÀcarbon bonds provides an especially attractive and straightforward method to directly introduce boryl and/or silyl groups into organic molecules by vic-or 1,4-diboration, [2] silylboration, [3] or disilylation. [4] Herein we report that bis(pinacolato)diboron (1) [5] and (dimethylphenylsilyl)(pinacolato)borane (2) [6] react with 1-halo-1-lithioalkenes 4, [7] alkylidene-type carbenoids available from 1,1-dihaloalkenes or 1-haloalkenes 3, to afford 1,1-diborylalkenes 5 [8] or 1-boryl-1-silylalkenes 6, [9] respectively. These products are readily converted into tri-or tetrasubstituted alkenes through various transition metal catalyzed carbonÀcarbon bond formations (Scheme 1).…”