26 research outputs found
Short Stereoselective Synthesis of the Phytophthora Universal Mating Hormone alpha 1 Using Lithiation/Borylation Reactions
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
Erratum: Synthesis of enantioenriched tertiary boronic esters from secondary allylic carbamates. Application to the synthesis of C30 botryococcene (Journal of the American Chemical Society (2012) 134 (7570-7575) DOI: 10.1021/ja303022d)
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