[BO₂]⁻ as a Synthon for the Generation of Boron‐Centered Carbamate and Carboxylate Isosteres

Abstract

Oxoborane carbamate and carboxylate analogues result from the in situ trapping of [BO 2 ] − produced by elimination of 2,3‐dimethyl‐2‐butene from a pinacolatoboryl anion.

Acid/Base-Free Acyclic Anionic Oxoborane and Iminoborane Bearing Diboryl Groups

“…In contrast to the well-known ketone compounds, oxoboranes (RBO) are prone to head-to-tail oligomerization because of the high polarity of the BO moiety. , Thus, monomeric oxoboranes are highly reactive and only observable in the gas phase, in argon matrix at low temperature, or by chemical trapping . In view of the electron-deficient boron center and the electron-rich oxygen atom, the employment of neutral or anionic ligands at the boron site and Lewis/Brønsted acids at the oxygen site have facilitated the isolation of base- and acid-stabilized oxoboranes. , Additionally, transition metal fragments have also been used by the groups of Braunschweig and Yamashita to stabilize the BO multiple-bonded compounds such as the base-free oxoboranes I (Chart a). In 2019, Aldridge and co-workers successfully isolated the first acid-free anionic oxoborane II , stabilized by a bulky N-heterocyclic ligand (Chart b) .…”

Boraiminolithium: An Iminoborane-Transfer Reagent

“…The subtle electronegativity difference between B and M (M = Pd, Pt, Rh) makes the B–M bonds in A and B highly covalent, and consequently they exhibit reactivities mimicking those of organic iminoboranes. Of note, species of the type RBNM remain elusive as stable compounds. − …”

A Terphenyl Supported Dioxophosphorane Dimer: the Light Congener of Lawesson's and Woollins’ Reagents

“…More recently, there has been an increasing awareness of the extent to which attractive dispersion forces between the ligands in terphenyl derivatives contributes to their structures and stability [16] . Recent work has shown that the action of DMAP upon a 1,3‐dioxa‐2‐elementolane derivative, LMgB(OCMe 2 ) 2 , can induce the ejection of alkenes and generate LMgBO 2 (DMAP) (L=[HC{H 3 CCN(2,6‐iPr 2 ‐C 6 H 3 )} 2 ]) [17] . We thus set out to investigate the capacity of terphenyl ligands to support dioxophosphoranes and of Lewis bases to induce ethene loss from substituted 1,3‐dioxa‐2‐phospholanes in the hope that access via mild conditions would prevent unwanted side reactivity of the ‐PO 2 moiety.…”

“…[16] Recent work has shown that the action of DMAP upon a 1,3-dioxa-2-elementolane derivative, LMgB(OCMe 2 ) 2 , can induce the ejection of alkenes and generate LMgBO 2 (DMAP) (L = [HC{H 3 CCN(2,6-iPr 2 -C 6 H 3 )} 2 ]). [17] We thus set out to investigate the capacity of terphenyl ligands to support dioxophosphoranes and of Lewis bases to induce ethene loss from substituted 1,3-dioxa-2-phospholanes in the hope that access via mild conditions would prevent unwanted side reactivity of the -PO 2 moiety. We herein report the reaction of Ar iPr4 P(OCH 2 ) 2 with either pyridine or DMAP affords the evolution of ethene at a reduced temperature relative to thermolysis and provides access to a light analogue of LR and WR, Ar iPr4 P(=O)(μ 2 -O) 2 P(=O)Ar iPr4 .…”