Reversible 1,1‐Hydroboration: Boryl Insertion into a CN Bond and Competitive Elimination of HBR₂ or RH

Abstract

Boranes with the general formula of HBR2 have been found to undergo a facile 1,1-hydroboration reaction with pyrido[1,2-a]isoindole (A), resulting in insertion of a BR2 unit into a CN bond and the formation of a variety of BN heterocycles. Investigation on the thermal reactivity of the BN heterocycles revealed that these molecules have two distinct and competitive thermal elimination pathways: HBR2 elimination (or retro-hydroboration) versus RH elimination, depending on the R group on the B atom and the chelate backbone. Mechanistic aspects of these highly unusual reactions have been established from both experimental and computational evidence. Adduct formation between HBR2 and A was found to be the key intermediate in 1,1-hydroboration of A.

Generation of an N→B Ladder‐type Structure by Regioselective Hydroboration of an Alkenyl‐Functionalized Quaterpyridine

“…Potential n‐type materials have also been generated through intermolecular coordination of strong Lewis acids, such as tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ), to conjugated polymers and oligomers . Examples of oligomeric systems that feature intramolecular N→B‐coordination, therefore, give rise to more well‐defined ladder‐type structures, have been investigated by groups of Yamaguchi (Scheme A , B ), Erker ( A ), Wang ( C ), and others . Compound C in particular has also been shown to be a versatile precursor for fully conjugated boron containing heteroacenes …”

Effects of the Substituents of Boron Atoms on Conjugated Polymers Containing B←N Units

“…The boron–nitrogen coordination bond (B←N) is one typical kind of Lewis acid/base pair . The intermolecular B←N Lewis pair has been employed to modulate molecular orbitals and thereby to tune absorption and fluorescence spectra of conjugated molecules and polymers . Our group has recently discovered that intramolecular B←N Lewis pair formation can significantly downshift LUMO/HOMO energy levels ( E LUMO / E HOMO ) of conjugated polymers .…”

Deviation from the anti-Markovnikov rule: a computational study of the regio- and stereoselectivity of diene hydroboration reactions

“…Hydroboration is one of the most central reactions pertaining to boron chemistry, due to its involvement in a wide array of chemical synthesis applications [1][2][3][4][5]. Hydroboration of alkenes has great importance because of the wide variety of uses of the resulting organoboranes, such as in Suzuki cross-coupling reactions and aldol condensation reactions [6][7][8].…”