Haloboration of Internal Alkynes with Boronium and Borenium Cations as a Route to Tetrasubstituted Alkenes**
نویسندگان
چکیده
Hail boration! 2-Dimethylaminopyridine-ligated dihaloborocations [X2B(2-DMAP)](+) with a strained four-membered boracycle were used for the haloboration of terminal and dialkyl internal alkynes (see scheme). Esterification then provided vinyl boronate esters as useful precursors to tetrasubstituted alkenes. Following mechanistic studies, the scope of the haloboration was expanded simply by variation of the amine. Pin = 2,3-dimethyl-2,3-butanedioxy.
منابع مشابه
Cyclic boronium and borenium cations derived from borabenzene-pyridine complexes.
A new class of boronium and borenium cations are prepared by reaction of pyridinium hydrochloride with pyridine stabilized borabenzene derivatives.
متن کاملCopper-catalyzed electrophilic carbofunctionalization of alkynes to highly functionalized tetrasubstituted alkenes.
Copper catalysts enable the electrophilic carbofunctionalization of alkynes with vinyl- and diaryliodonium triflates. The new process forms highly substituted alkenyl triflates from a range of alkynes via a pathway that is opposite to classical carbometalation. The alkenyl triflate products can be elaborated through cross-coupling reactions to generate synthetically useful tetrasubstituted alke...
متن کاملCopper(I)-catalyzed formal carboboration of alkynes: synthesis of tri- and tetrasubstituted vinylboronates.
The first copper-catalyzed formal carboboration of alkynes, in which a C-B bond and a C-C bond are created in a single catalytic cycle, is presented. The reaction proceeds with high regioselectivity and syn-stereoselectivity to form tri- and tetrasubstituted vinylboronic esters from commercially available bis(pinacolato)diboron. A subsequent cross-coupling reaction gives access to highly substi...
متن کاملsyn-1,2-Carboboration of Alkynes with Borenium Cations
The reaction of 8-(trimethylsiloxy)quinoline (QOTMS) with BCl3 and (aryl)BCl2 forms QOBCl2 and QOBCl(aryl). The subsequent addition of stoichiometric AlCl3 follows one of two paths, dependent on the steric demands of the QO ligand and the electrophilicity of the resulting borenium cation. The phenyl- and 5-hexylthienylborenium cations, QOBPh(+) and QOBTh(+), are formed, whereas QOBCl(+) is not....
متن کاملSynthesis and structural characterization of a stable dimeric boron(II) dication.
A number of boronium ions with the general formula [R2BL2] + (where L is a donor, such as an amine), some borenium [R2BL] , and even borinium [R2B] + ions have been synthesized and structurally characterized. In all these compounds, boron has a formal oxidation state of + III. In addition to the academic interest in the bonding properties in these species, some of them have found application as...
متن کامل