Chemo-, Regio-, and Stereoselective Copper(II)-Catalyzed Boron Addition to Acetylenic Esters and Amides in Aqueous Media

Abstract

Aqueous conditions were developed for conducting an open-to-air, copper(II)-catalyzed addition of pinBBdan to alkynoates and alkynamides. The simple and mild β-borylation protocol proceeds in a remarkably chemo-, regio-, and stereoselective fashion to afford 1,8-diaminonaphthalene protected (Z)-β-boryl enoates and primary, secondary, and tertiary enamides in good to excellent yields. These reactions demonstrate a high tolerance toward a variety of alkyl, aryl, and heteroatom functional groups and provide convenient access to a diverse range of vinylboronic acid derivatives.

Enantioselective synthesis of cis-hydrobenzofurans bearing all-carbon quaternary stereocenters and application to total synthesis of (‒)-morphine

“…Starting from commercially available 3-butyn-1-ol 3 , the protection of the primary alcohol with benzyl group and subsequent treatment with N -methoxy- N -methylcarbamoyl chloride 34 afforded the Weinreb amide 5 . The boronation 35 of 5 with B 2 (Pin) 2 followed by Suzuki coupling with aryl bromide 2 (prepared from 2-bromo-6-methoxyphenol 4 ) furnished tri-substituted aromatic compound 6 . Final addition with methylmagnesium bromide followed by deprotection of the acetal group provided the desired precursor 7 .

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Copper-boryl mediated organic synthesis

“…Replacing the B 2 pin 2 with the mixed diboron danBBpin (9), allows selective transfer of the Bdan moiety and hence complementary chemistry to the normal Bpin products (Scheme 27iii). 119 However, the use of 10% ethanol in water or 2% TPSG detergent is required to solubilize the diboron reagent. Coppermediated borylations can also occur across carbon-heteroatom unsaturated systems in a 1,2-addition fashion, with examples of reactions with aldehydes, 120,121 ketones, 122 and aldimines 123 to afford a-alkoxyand a-amino-boronates (Scheme 28).…”

Copper‐Catalyzed B(dan)‐Installing Allylic Borylation of Allylic Phosphates

“…Since our report on the copper‐catalyzed Markovnikov hydroboration of terminal alkynes, a borylcopper species [Cu−B(dan)] has been the linchpin of the catalytic B(dan)‐installing reactions ,. In addition to the well‐established addition reactions across unsaturated carbon−carbon bonds such as borylstannylation, carboboration, aminoboration and conjugate addition, borylative substitution of organic halides, also occurs smoothly, demonstrating that Cu−B(dan) can act as a boron nucleophile. Although various R−B(dan) (R=alkyl, alkenyl, aryl and allyl) are directly accessible by the substitution, a representative problem awaiting solution is low α/γ‐selectivity in the allylic borylation of allylic halides (Scheme ), which should result from a radical pathway operative therein.…”