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A highly efficient regio- and stereoselective method for allenoate borylation has been developed. Using CuCl and bis(pinacolato)diboron in methanol, a variety of allenoates underwent β-boration and α-protonation to afford the corresponding Z -β,γ-unsaturated β-boryl esters under mild conditions with up to 81% yields.

Within these, Modes B A b and B C b , in which the boron atom acts as a Lewis acid, have been widely explored, [6] SP , sp [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] whereas reports on the phosphorus atom acting as a Lewis base (Mode B B b ) are scarce. [37] In Ph SB 2 sb PBpin, despite the presence of tricoordinate boron and phosphorus centers, there is negligible -dative interaction between the phosphorus lone pair and the p-orbital on the boron. Keywords: pinacol diphenylphosphinoboronate; boroles; borafluorenes; antiaromaticity; Lewis acid EN pinacol diphenylphosphinoboronate boroles borafluorenes antiaromaticity Lewis acid 2193 2196 4 10/31/23 20231127 NES 231127 Graph Phosphinoboranes [1][52][2] (R SB 2 sb P-BR SB 2 sb ) feature trivalent and tricoordinate P and B atoms linked covalently and are valence isoelectronic with aminoboranes (R SB 2 sb N-BR SB 2 sb ; Scheme 1a). Upon coordination, the P(1)-B(2) bonds of the Ph SB 2 sb PBpin elongate slightly [ B 1 b : 1.953(2) A , B 2 b : 1.9432(18) A , cf. free Ph SB 2 sb PBpin: 1.9274(14) A ]. [Extracted from the article]

We report the first trans phosphinoboration of internal alkynes. With an organophosphine catalyst, alkynoate esters and the phosphinoboronate Ph2P‐Bpin are efficiently converted into the corresponding trans‐α‐phosphino‐β‐boryl acrylate products in moderate to good yield with high regio‐ and Z‐selectivity. This reaction operates under mild conditions and demonstrates good atom economy, requiring only a modest excess of the phosphinoboronate. X‐ray crystallography experiments allowed structural assignment of the unprecedented and densely functionalized (Z)‐α‐phosphino‐β‐boryl acrylate products. [ABSTRACT FROM AUTHOR]

The NaOtBu‐catalyzed mixed 1,1‐diboration of terminal alkynes using the unsymmetrical diboron reagent BpinBdan (pin = pinacolato; dan = 1,8‐diaminonaphthalene) proceeds in a regio‐ and stereoselective fashion affording moderate to high yields of 1,1‐diborylalkenes bearing orthogonal boron protecting groups. It is applicable to gram‐scale synthesis without loss of yield or selectivity. The mixed 1,1‐diborylalkene products can be utilized in Suzuki–Miyaura cross‐coupling reactions which take place selectivly at the C–B site. DFT calculations suggest the NaOtBu‐catalyzed mixed 1,1‐diboration of alkynes occurs through deprotonation of the terminal alkyne, stepwise addition of BpinBdan to the terminal carbon followed by protonation with tBuOH. Experimentally observed selective formation of (Z)‐diborylalkenes is supported by our theoretical studies. [ABSTRACT FROM AUTHOR]

Copper-catalyzed asymmetric conjugate additions are powerful reactions that allow the formation of single-enantiomer building blocks in a few steps. However, highly enantioselective conjugate addition to five-membered-ring substrates is more challenging and is often neglected. Here, we report catalytic asymmetric 1,4-addition of alkylzirconocenes, formed in situ from readily available alkenes, to cyclopent- 4-ene-1,3-dione monoacetals. Good to high enantioselectivities are observed and the procedure tolerates various functional groups. [ABSTRACT FROM AUTHOR]

Copper(II)-catalyzed silylation of substituted alkynylcarbonyl compounds was investigated. Through the activation of Me2PhSiBpin in water at room temperature and open atmosphere, vinylsilanes conjugated to carbonyl groups are synthesized in high yield. A surprising diastereodivergent access to olefin geometry was discovered using a silyl conjugate addition strategy: aldehydes and ketones were Z selective while esters and amides were exclusively transformed into the E products. [ABSTRACT FROM AUTHOR]

Using bis(pinacolato)diboron, catalytic amounts of CuII, and various amine bases in water under atmospheric conditions at rt, acyclic and cyclic α,β-unsaturated ketones and esters are β-borylated in up to 98% yield. Mechanistic investigations using UV–vis spectroscopy, 11B NMR, and solvent kinetic isotope effect suggest that the role of the amine is not only to coordinate to CuIIbut also to activate a nucleophilic water molecule to form the reactive sp2–sp3diboron complex. [ABSTRACT FROM AUTHOR]

A two-step procedure for deprotection of alkylpinacolyl boronate esters via transesterification with diethanolamine followed by hydrolysis was successfully developed with the advantages of tolerance to various functional groups, short reaction time, and ease of product isolation. [ABSTRACT FROM AUTHOR]

This facile borylation reaction proceeds in a regio-, E/Z-, and chemoselective manner to afford high yields of (Z)-β-boryl-α,β-unsaturated esters exclusively. [ABSTRACT FROM AUTHOR]