Organoboron-Co Compounds

The route is limited by its inability to include haloalkylboranes (RjBCl, RBClj, etc.) e.g., from PhjSnLi and BCI3, RBClj or R BCl, no tin-boron compounds are detected, PhgSnj being the major product . Compounds R Sn(BR 2)4- are best obtained from organoboron-Co compounds ( 5.3.17.3.1). 

Organoboron-Co compounds are precursors to metal-boron bonds as established for Sn (see 5.3.17.3.1) and provide a RT route to otherwise inaccessible organoboron-Pb compounds ... 

Organoboron compounds react with carbon monoxide, which is the simplest carbonyl compound, under conditions of high temperature and pressure. Many reactions with transition metal compounds such as Fe, Ni and Co compounds are known. However, few carbonylations with main group metal compounds proceed. These reactions can be applied to, for example, the carbonylation shown in eq. (6.18) [9,34,35]. 

In addition, Wipf and co-workers104 have used silver(i)-catalyzed addition of zirconocenes to 3,4,6-tri-O-benzyl-D-glucal epoxide 93 for the stereoselective synthesis of a-C-glucosyl compounds 95 and 96 following a similar mechanism as in the reaction with organoaluminium and organoboron reagents (Scheme 32). 

There is a vast array of carbon-carbon-bond-forming reactions involving organoboron compounds. This section covers transfer reactions of carbon moieties from boron to an adjacent carbon. Examples include the transfer of CO, CN, carbanions derived from dichloromethyl methyl ether and dichloromethane, and allyl groups in reactions of allylic boranes with aldehydes. 

The structural analysis of Gp TiMe2(0-2,6-Pr12G6H3) and Gp TiMe(0Tf)(0-2,6-Pr12G6H3) has been described and the effect of the organoboron compounds as co-catalysts in 1-hexene polymerizations has been studied.867 The molecular structures of CpTiCl2(OCy),865 CpTiCl OPr1),868 and CpTiCl2[0-l-(4-methoxo-phenyl)cyclohexyl]869 have been determined. 

Methods to form fluorescein and rhodamine dyes typically feature high-temperature condensation reactions that are not readily adapted to form small libraries of derivatives. Burgess and co-workers developed borylation, Suzuki, and Sonogashira reactions involving bromo derivatives of fluorescein and rhodamine [86]. Organoboron compounds, biaryls, and alkynes were readily synthesized by... 

The metal-catalyzed addition reaction of organoboron compounds have not yet been well developed, but the reaction of NaBPh or arylboronic adds with enones in the presence of Pd(OAc)2 and NaOAc or SbClj was recently reported by Uemura and his co-workCTS. The reaction was proposed to proceed through the oxidative addition of the C-B bond to the Pd(0) species however, another probable process, the transmetalation to transition metals, may allow a similar catalytic transformation by the use of organoboronic acids. We report here the 1,4-addition reaction of organoboronic adds to a,P-unsaturated ketones or esters and 1,2-addition to aldehydes or imines catalyzed by a (acac)Rh(CH2=CH2)2/phosphine complex, which may involve the B-Rh transmetalation as the key step. 

Meanwhile, Lei and his colleagues discovered a novel protocol that makes use of air as an oxidant at low temperatures [111], Using a balloon pressure of CO/air mixture, arylboronates were converted into the corresponding esters in good yields (Scheme 8.29). This was the first example that could apply simply air in the oxidative carbonylation of organoboron compounds with alcohols. 

Very recently, Taylor and co-workers (241) demonstrated that organic borinic acids are remarkably efficient catalysts for the direct aldol reaction pyruvic acids and aldehydes in aqueous media. The ability of organoboron compounds to activate pyruvic acids to form dioxoborolanone intermediates in a selective fashion in water thus enabled the development of a highly efficient boron-catalyzed direct aldol reaction (Scheme 61). 

In hydroboration, in contrast, no isomerization is observed. Not only can the 16e alkylzirconium species be converted into the same products that an organoboron compound would give, but under CO an insertion takes place to give the acyl. This acyl can subsequently be converted into a variety of organic carbonyl compounds, such as the acyl halides by halogen oxidation, or the ester by bromine oxidation in an alcohol solvent. 

Further (c/. Vol. 1, p. 89) Russian work on fluoroalkenylcarbaboranes has been reported (see p. 60), fluoroalkylborates have been synthesized via reaction of hexafluoroacetone and related ketones with boron halides, organoboron halides, or alkylthioboranes (see p. 257), and from perfluoro-alkyl hypochlorites (see p. 264), CFj-S—B compounds have been prepared (see p. 270), and conductivity studies on the complex acid HBfOaC CFj) and its caesium salt have been described. Attempts to isolate the tristri-fluoroacetate B(02C CF3)a from products of the reaction systems B(OH)3-(CFs CO) , BCl3-(CF9 CO)jO-n-pentane, and BCl3-CF3-C02H-n-pentane have yielded only I(CF3 C0s)2B]20 or [(CF3 C02)2B]30-B(02C CF3)3 mixtures (c/. ref. 58). 

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