O₂‐Mediated Oxidation of Aminoboranes through 1,2‐N Migration

Abstract

In analogy to the classical reaction of CÀBb onds with peroxides,t he first oxidative functionalization of aminoboranes through a1 ,2-N migration was realized.R eadily available aliphatic nitro compounds are thereby transformed into N-and O-functionalized hydroxylamines in as ingle synthetic operation. Addition of hazardous peroxides is avoided. Instead, the insertion of O 2 ,a st he terminal oxidant, into Zn À Cb onds provides the necessary peroxides.T he required zinc organyls,i nt urn, are formed through ab oronto-zinc exchange,f rom an organoboronic ester byproduct of the nitro-to-aminoborane transformation.Scheme 1. Oxidation of organoboranes (a) and aminoboranes (b).

Catalyst‐Free Reductive Coupling of Aromatic and Aliphatic Nitro Compounds with Organohalides

“…Hence,arapid boron to zinc transmetalation [17] is promoted, and feeds the boronic ester R 1 Bpin back into the reaction sequence. [18] Confirming the participation of B and nitrenoid II in the partial reduction of the nitro group, as tepwise reaction of 1a with ap reformed borate, [B 2 pin 2 ·R 1 ] À ,w as also analyzed by time-resolved 11 B-{ 1 H} NMR analysis (see the Supporting Information).…”

“…This step initializes the two-step reduction sequence by addition of the nucleophilic Bpin fragment in A to the nitro groupsO,generating the borylated dihydroxylamine anion B.U pon reaction of B with more B 2 pin 2 ,n itrenoid II is formed. [18] Confirming the participation of B and nitrenoid II in the partial reduction of the nitro group, as tepwise reaction of 1a with ap reformed borate, [B 2 pin 2 ·R 1 ] À ,w as also analyzed by time-resolved 11 B-{ 1 H} NMR analysis (see the Supporting Information). [11] These investigations indeed confirm the formation of A, D, and an increasing amount of pinBO À .Asignal for the byproduct of the first reduction step,t he boronic ester R 1 Bpin, which remains after the transfer of the nucleophilic boron moiety from A was not observed throughout the reaction.…”