Reagent-Controlled Lithiation–Borylation

Pd-Catalyzed Conjunctive Cross-Coupling between Grignard-Derived Boron “Ate” Complexes and C(sp2) Halides or Triflates: NaOTf as a Grignard Activator and Halide Scavenger

“…With these reagents, powerful stoichiometric asymmetric homologation reactions have enabled a broad array of C–C and C–heteroatom bond constructions directly from the organoboronic ester starting materials. 3 Similarly, many catalytic processes have been developed that provide access to chiral organoboronic esters from simple building blocks. 4 In this vein, our laboratory recently described a catalytic conjunctive cross-coupling reaction (Scheme 1) that operates on alkenyl boronic ester-derived "ate" complexes and produces enantiomericallyenriched alkyl boronic esters in an efficient fashion.…”

Catalytic conjunctive cross-coupling enabled by metal-induced metallate rearrangement

“…These processes are common (9) for transformations where the “A” group is a carbon, nitrogen, or oxygen atom, and less common but still established for sulfur and phosphorus (10,11). Because of the stereospecific nature of the above-described processes, stereoselectivity in metallate shifts is generally subject to substrate control (12) though Jadhav and Man reported an example with selectivity dictated by a chiral catalyst (13). 1,2-Metallate rearrangements from boron to sp (14) and sp 2 (15) hybridized carbons often require the addition of an external electrophilic activator (Fig.…”

Formation of Olefins by Eliminative Dimerization and Eliminative Cross‐Coupling of Carbenoids: A Stereochemical Exercise

“…[26] Thee ase of generating carbamoyloxy-based carbenoids in this manner, and their high configurational stability and comparative chemical robustness,explains the popularity and effectiveness of lithiated carbamates in the stereospecific reagent-controlled homologation (StReCH) [8a] of boronic esters. [27,28] Replacement of the carbamate metalation director with a2 ,4,6-triisopropylbenzoyloxy( TIBO) group [29] enables the generation of stereodefined non-benzylic/non-allylic secondary alkyllithium compounds (e.g. entry 14).…”

“…117). Theformer carbenoids have proven to be superior reagents for the chain extension of boronic esters, [27,28,37] and both types of substrates are conveniently made from simple carbamate precursors,as highlighted in Section 2. Depending on the reaction conditions employed and the kind of boronic ester used, the Blakemore alkene synthesis can be terminated by either an anti-orasyn-mode elimination step.For example,addition of boron carbenoid (S)-117 [31] to ap re-generated solution of lithium carbenoid (S)-116 in diethyl ether gave the putative ate complex lk-118,w hich rearranged upon warming to give the pre-elimination adduct lk-119 as essentially as ingle isomer (Scheme 20).…”