Asymmetric organocatalytic diboration of alkenes

Abstract

The use of chiral alcohols to form the Lewis acid-base *RO(-)→ bis(pinacolato)diboron adduct, in situ, provides an opportunity to induce asymmetry in the organocatalytic diboration of alkenes and complements the well established transition metal-mediated enantioselective diboration.

Asymmetric Synthesis of Secondary and Tertiary Boronic Esters

“…[165] In the system reported by Fernandez, methoxide anion (generated from the crucial base and methanol additives) is proposed to activate the diboron reagent, generating an sp 2sp 3 diboron species.Inalater publication, Fernandez was able to achieve moderate levels of enantioselectivity (up to 42 % ee)for the diboration of unactivated terminal olefins,through the use of chiral alcohol additives. [166] Thec hiral alkoxides presumably interact with the diboron reagent, allowing for moderate level of asymmetric induction. Morken and coworkers later considerably improved the asymmetric metalfree diboration of alkenes through the use of chiral diols.…”

Transition‐Metal‐Free Borylation of Alkynes and Alkenes

“…Song presented a transition‐metal‐free method applied in borylation of terminal alkynes to provide alkylboronates . Fernández's and Morken's group reported the transition‐metal‐free enantioselective diboration of alkenes using chiral reagents.…”

Theoretical study on homolytic B–B cleavages of diboron(4) compounds

“…3 In general, the synthetic reactions involving diboron(4) compounds such as B 2 X 4 , B 2 (NR 2 ) 4 , B 2 (alkyl) n , B 2 (OR) 4 , etc. mainly include borylation reactions, [4][5][6][7][8][9][10][11] diboration reactions, [12][13][14][15][16][17][18] borylative cyclization reactions, [19][20][21] borylative ring opening reactions, [22][23][24][25][26][27] boracarboxylation reactions, 28 hydroboration and carboboration reactions, 29-32 etc. For instance, Miyaura et al 33,34 developed the borylation reactions using dialkoxyboranes or diboron ( 39 reported the rhodium(I)-catalyzed diboration reaction of Estyryl boronate esters with B 2 cat 2 , in which the 1,1,1-triborylalkane is the dominant product.…”

“…Szabó et al 41 studied the borylative ring opening reaction of substituted vinylcyclopropanes and vinyl aziridines with tetrahydroxydiboron catalyzed by palladium. Besides the above exemplied reactions catalyzed by the transitional-metal catalyst, there are also many researches on the reactions involving diboron (4) compounds under the transition-metal-free condition, such as borylation reactions, 10,11 diboration reactions [16][17][18] and borylative ring opening reactions, [25][26][27] etc.…”