Recent advances in the synthesis and reactivity of MIDA boronates

Abstract

Organoboron compounds have wide-ranging applications in synthetic methodologies, natural products, and bioactive molecule synthesis. The sensitivity of boronic acid toward most synthetic reagents makes it necessary to introduce a protecting...

Modular Access to Diverse Amphoteric α-Boryl Aldehydes or Borylated Heterocycles via Photoredox Catalysis

“…The organoboron compounds are among the most frequently used synthetic intermediates in organic synthesis, medicinal chemistry, and material science . Among those, a class of stable α-boryl aldehydes, which were elegantly introduced independently by the group of Yudin and Burke in 2011, are important amphoteric synthetic intermediates that act as linchpins in organic synthesis (Scheme A). The incorporation of N -methyliminodiacetic acid (MIDA) or pinene-derived iminodiacetic acid (PIDA) as a ligand to the boron center prevents the facile C-to-O boryl migration, , thus enabling the isolation of α-boryl aldehydes with great synthetic potential.…”

“…However, these methods are generally focused on the syntheses of α-boryl ketones, esters, or amides. – The rapid and efficient access to diverse functionalized α-boryl aldehydes has been challenging. Current approaches to these important building blocks typically rely on the oxidative processes (Scheme B), such as epoxidation – or dihydroxylation/acid-promoted rearrangement sequence of vinyl MIDA boronates (eqs 1–4), TBHP-mediated Wacker oxidation of a vinyl MIDA boronate (eq 5), ozonolysis of an allylic MIDA boronate (eq 6), as well as oxidation of a β-MIDA boronate containing primary alcohol (eq 7) . Despite these advances, issues such as lack of product diversity and functional group compatibility that might be induced by the requirement of oxidative conditions still need to be addressed.…”

Synthesis of α-Boryl Ketones via Hydration or Oxidation of B(MIDA)-Decorated Alkynes

“…The radical hydroboration of α,β-unsaturated carbonyl compounds or alkenyl triflates, with different initiators, provides another efficient route (Scheme b). Taking advantage of the notable stability of N -methyliminodiacetyl boronates (B(MIDA)s), Yudin and Burke independently realized the synthesis of α-boryl aldehydes (Scheme c) via a Lewis acid-promoted rearrangement of oxiranyl B(MIDA)s, which were prepared via a chemoselective oxidation of alkenyl B(MIDA)s. Research work from us showed that the alkenyl B(MIDA)s can be directly subjected to radical oxygenation reactions, producing diverse halogenated α-boryl carbonyl products (Scheme c) . On the other hand, a palladium-catalyzed regioselective Wacker oxidation of alkenyl B(MIDA)s also allowed the straightforward synthesis of α-borylated ketones.…”

Divergent Synthesis of 1,1-Carbonyl Amino Alkyl Borons from Indoles

“…Therefore, indoles with a boron moiety on the C2 position should be a suitable substrate to achieve our hypothesis. Herein, we disclose a meaningful strategy for the construction of 1,1-carbonyl amino alkyl borons from 2-BMIDA indoles under oxidative conditions, which features operational simplicity, broad substrate scope, and valuable products. In addition, Witkop oxidation and Baeyer-Villiger oxidation also can be achieved in this reaction system to afford stable acyloxyboronate products when C3-substituted 2-BMIDA indoles act as substrates (Figure C).…”