Accessing highly substituted indoles via B(C6F5)3-catalyzed secondary Alkyl Group Transfer

Herein, we report a synthetic method to access a range of highly substituted indoles via the B(C6F5)3-catalyzed transfer of 2° alkyl groups from amines. The transition-metal-free catalytic approach has been demonstrated across a broad range of indoles and amine 2° alkyl donors, including various substituents on both reacting components, to access useful C(3)-alkylated indole products. The alkyl transfer process can be performed using Schlenk line techniques in combination with commercially available B(C6F5)3·nH2O and solvents, which obviates the requirement for specialized equipment (e.g., glovebox)

Electron deficient borane-mediated hydride abstraction in amines: stoichiometric and catalytic processes

The manipulation of amino C–H bonds has garnered significant interest from the synthetic community due to its inherently high atom, step and redox economy. This Tutorial Review summarises the ability of boranes to mediate hydride abstraction from α-amino and γ-amino conjugated C–H bonds. Borane-mediated hydride abstraction results in the generation of reactive iminium hydridoborate salts that participate in a variety of stoichiometric and catalytic processes. The reactions that have utilised this unusual reactivity include those that manipulate amino scaffolds (including dehydrogenation, racemisation, isomerisation, α- and β-functionalisation, and C–N bond cleavage) and those that use amine-based reagents (transfer hydrogenation, and alkylation)

Recent advances in catalysis using organoborane-mediated hydride abstraction

C–H functionalization is widely regarded as an important area in the development of synthetic methodology, enabling the design of more time- and atom-efficient syntheses. The ability of electron-deficient organoboranes to mediate hydride abstraction from α-amino C–H bonds is therefore of great interest, as the reactive iminium and hydridoborate moieties generated are able to participate in a range of synthetically useful transformations. In this review, we cover the recent advances made in organoborane-mediated hydride abstraction, and focus on the catalytic applications of electron-deficient boranes in α- or β-functionalization, α,β-difunctionalization, and the dehydrogenation of amines

Stereospecific conversion of alcohols into pinacol boronic esters using lithiation-borylation methodology with pinacolborane

The synthesis of primary and secondary pinacol boronic esters via lithiation–borylation of carbamates and benzoates with pinacolborane is described. This new protocol enables the highly selective synthesis of enantioenriched and geometrically defined boronic esters that cannot otherwise be accessed by alternative methodologies

Correction to Synthesis of Enantioenriched Tertiary Boronic Esters from Secondary Allylic Carbamates. Application to the Synthesis of C30 Botryococcene

Correction to Synthesis of Enantioenriched Tertiary Boronic Esters from Secondary Allylic Carbamates. Application to the Synthesis of C30 Botryococcen

Synthesis of Enantioenriched Tertiary Boronic Esters from Secondary Allylic Carbamates. Application to the Synthesis of C30 Botryococcene

Enantioenriched secondary allylic carbamates have been deprotonated with <i>s</i>BuLi and reacted with boronic esters. In contrast to other electrophiles, high α-selectivity was observed and the boronate complexes were formed with almost complete retention of stereochemistry. The boronate complexes underwent a stereospecific 1,2-migration leading to tertiary allylic boronic esters with high <i>er</i> (>98:2). The scope of the reaction has been explored and found to embrace a broad range of both allylic carbamates and boronic esters. The methodology has been applied to an eight-step, stereoselective synthesis of each of the diastereoisomers of C30 botryococcene