Synthetic Chemistry with Lewis Acidity‐Diminished B(aam) and B(dan) Groups: Borylation Reactions and Direct Cross‐Couplings

Abstract

This review describes recent advances in the synthesis of anthranilamide/1,8‐diaminonaphthalene‐substituted organoboron compounds with diminished boron Lewis acidity via catalytic B(aam)‐ and B(dan)‐installing borylation reactions, which have attracted growing attention especially in the last five years owing to their unique reactivity, regioselectivity, and the outstanding stability toward air and moisture of organoboron compounds obtained therefrom. Direct Suzuki–Miyaura cross‐couplings with R–B(aam)/B(dan), which were believed to be wholly unreactive until recently, are also discussed.

Regioselective trans‐Hydrostannation of Boron‐Capped Alkynes

“…In the present context, however, one has to keep in mind that the use of −B(aam) derivatives for Suzuki‐Miyaura cross coupling reactions is uncommon. Yet, a recent investigation provides encouraging precedent in that it showed that aryl‐B(aam) derivatives allow for direct cross coupling without need for prior unmasking of the corresponding boronic acid [35,41] . The results compiled in Scheme 4 do not only confirm this result: it is actually stunning to find that the Suzuki‐Miyaura reaction outcompetes a Stille cross coupling under the chosen conditions; [54] in the basic aqueous medium, protodestannylation did not interfere.…”

“…Yet, a recent investigation provides encouraging precedent in that it showed that aryl-B(aam) derivatives allow for direct cross coupling without need for prior unmasking of the corresponding boronic acid. [35,41] The results compiled in Scheme 4 do not only confirm this result: it is actually stunning to find that the Suzuki-Miyaura reaction outcompetes a Stille cross coupling under the chosen conditions; [54] in the basic aqueous medium, protodestannylation did not interfere. This somewhat unusual yet gratifying "inverse" order of reactivity brings functionalized alkenylstannanes into reach in isomerically pure form which would be difficult to prepare otherwise.…”

“…Indeed, the corresponding À B(aam) analogue 1 e (aam = anthranilamidato) allowed all of these issues to be addressed. Although some virtues of the benzo-1,3,2-diazaborininone ring system have been clearly pointed out in the literature, [35,[38][39][40][41][42] it continues to be underutilized. [43] In the present context, this particular boron heterocycle served our purpose very well: alkynyl-B(aam) derivatives such as 1 e are fairly easy to make on scale (see below) and bench-stable for extended periods of time.…”

Primary trifluoroborate-iminiums enable facile access to chiral α-aminoboronic acids via Ru-catalyzed asymmetric hydrogenation and simple hydrolysis of the trifluoroborate moiety

“…Organoboron compounds 1 play a pivotal role in synthetic organic chemistry, where they have enabled a myriad of useful transformations 2–4 and have also been used in the field of materials science. 5 The most advantageous application of organoboron compounds was achieved in medicinal chemistry 6 where several boron-containing drugs reached the market in the last two decades.…”

Borylation and Stannylation Reactions with Tuning of Lewis Acidity

“…[3,4] In this context, we have been involved in developing new borylation and stannylation reactions; in the case of the borylation, our attention has particularly been directed toward diminishing the inherent Lewis acidity of boron moieties to be installed by employing naphthalene-1,8-diaminato (dan) or anthranilamidato (aam) as a substituent on boron centers. [5] In view of the boron Lewis acidity, which strongly impacts reactivity and regio/stereoselectivity in borylation reactions, we envisaged that the use of B(dan)-or B(aam)-based reagents with diminished boron-Lewis acidity could bring about a drastic change in behavior in the borylation reactions, and properties of organoboranes obtained therefrom. On the other hand, since organotrialkylstannanes, used mainly as stannylating reagents in this study, basically exhibit little Lewis acidity, we have been interested in increasing the tin-Lewis acidity by electron-withdrawing inductive effect of organic groups on tin center, thus leading to unique reactivities and stannylation reactions therewith.…”