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Metalation of 2-alkynes with BuLi followed by treatment with diisopinocampheylchloroborane and warming to room temperature gives exclusively the propargylic diisopinocampheylboron derivatives. These on treatment with aldehydes at −100 °C in ether, provide alkyl- and aryl-substituted α-allenic alcohols in high regiomeric and enantiomeric purities.

A convenient, one-pot synthesis of unsymmetrical ketones has been developed making use of the in situ reduction — hydroboration reactions of readily prepared and stable (±)-isopinocampheyldichloroborane.

A quantitative study was made of the preparation of the optically pure borane reagent, isopinocampheylchloroborane (IpcBHCl), potentially valuable for asymmetric hydroboration. IpcBHCl (87−90%) in equilibrium with 5−6.5% of IpcBCl2 and IpcBH2, respectively, can be prepared conveniently by a number of relatively simple operations: (1) the reaction of isopinocampheylborane (IpcBH2) with anhydrous hydrochloric acid (HCl) in ethyl ether (EE); (2) the reaction of stoichiometric amounts of IpcBH2 with isopinocampheyldichloroborane (IpcBCl2) in EE; and (3) the reduction of IpcBCl2 with trimethylsilane (Me3SiH) or lithium aluminum hydride (LAH) in EE. The reduction of IpcBCl2 with Me3SiH in pentane proceeds extremely slowly to provide the desired reagent, IpcBHCl. However, in EE, the reduction proceeds much faster, providing an equilibrium mixture of 90% IpcBHCl, 5% IpcBH2, and 5% IpcBCl2. We also investigated the reduction of IpcBCl2 with Me3SiH in pentane and dichloromethane (CH2Cl2) in the presence of known a...

Optically active homoallylic alcohols of exceptionally high enantiomeric purity (98-≥99% ee) readily available via asymmetric allylboration were converted into p-nitrobenzoate esters and subjected to hydroboration followed by oxidation with CrO 3 in aqueous acetic acid (10% H 2 O) to obtain the corresponding carboxylic acids with the same number of carbon atoms. The protecting ester group was hydrolyzed and the product lactonized in situ to the γ-substituted γ-butyrolactones (5) (R=Me, Pr, i-Pr, t-Bu, Ph, (E)-CH=CHCH 3 ) usually without racemization and in good yields

Acyl-substituted methyl radicals (RCOCH 2 . ; R=H, Me, Ph), generated by photolysis of RCOCH 2 -HgCl, add to alkenes, enol ethers, or vinyl sulfides to give adduct radicals that are readily trapped by PhSSPh to yield a three-component condensation product. The presence of an alkali metal carbonate is crucial in preventing side reactions resulting in the conversion of the mercurial to RCOCH 3 by PhSH formed in the photolysis

Acyl-substituted methyl radicals (RCOCH 2 . ; R=H, Me, Ph), generated by photolysis of RCOCH 2 -HgCl, add to alkenes, enol ethers, or vinyl sulfides to give adduct radicals that are readily trapped by PhSSPh to yield a three-component condensation product. The presence of an alkali metal carbonate is crucial in preventing side reactions resulting in the conversion of the mercurial to RCOCH 3 by PhSH formed in the photolysis

For the first time, a highly efficient and direct oxidation of a variety of organoborane intermediates into carboxylic acids has been demonstrated, without an increase or decrease of carbon atoms. Synthetically useful procedures have been developed for the ready conversion of representative terminal alkenes into carboxylic acids via oxidation of the organoboranes obtained by hydroboration of the terminal alkenes

Readily prepared and stable (+/-)-isopinocampheyldichloroborane [(+/-)-IpcBCl(2)] was conveniently used for the stepwise hydroboration of two different alkenes using the in situ reduction-hydroboration protocol to give mixed trialkylboranes, IpcBR(1)R(2). Convenient elimination of alpha-pinene from these trialkylboranes by treatment with an aldehyde, RCHO, provided the borinate ester, R(1)R(2)BOCH(2)R. This intermediate was readily converted into the unsymmetrical ketones, R(1)COR(2), in high yields and purity, by an established method. This methodology was successfully applied to the synthesis of enantiomerically pure spiroketals using optically pure TBS ether protected homoallylic alcohols as the alkenes for stepwise hydroboration.