Stereocontrolled Synthesis of Tetrasubstituted Olefins

Abstract

was directed toward the efficient construction of single isomer tetrasubstituted olefins. Scheme 1. Representative Use of an NOE Network To Determine Regio-and Stereochemistry Scheme 2. A Surprising Result Requiring Careful Product Identification Scheme 3. Regio-and Stereoisomeric Possibilities from Carbometallation Processes

Ni-Catalyzed Divergent Cyclization/Carboxylation of Unactivated Primary and Secondary Alkyl Halides with CO2

“…12 Herein, we report a mild and user-friendly reductive cyclization/carboxylation of unactivated alkyl halides with CO 2 en route to elusive tetrasubstituted olefins (Scheme 2, path b). 13 In sharp contrast with syncarbometallation techniques of stoichiometric, welldefined and, in many instances, air-sensitive organometallics (Scheme 2, path a), 14 our protocol is characterized by its exquisite chemoselectivity profile while obviating the need for sensitive species. Importantly, this transformation is distinguished by an unconventional divergence in syn/anti-selectivity that can be easily dictated by the ligand backbone or substrate utilized.…”

Haloboration of Internal Alkynes with Boronium and Borenium Cations as a Route to Tetrasubstituted Alkenes

“…Thus, alternative regio-and stereospecific methods are needed, particularly for subsequent use in the formation of tetrasubstituted alkenes, [5][6][7] as the production of these important biologically active compounds as single isomers by classical methods is challenging. [8] One simple approach to trisubstituted vinyl boronates is the functionalization of internal alkynes by metal-catalyzed 1,2-carboboration [9][10][11][12][13] and 1,1-carboboration. [14] The introduction of two selectively transformable moieties onto an internal alkyne should enable ready access to tetrasubstituted alkenes by successive cross-coupling reactions.…”

Synthesis of Trisubstituted Alkenylstannanes through Copper‐Catalyzed Three‐Component Coupling of Alkylboranes, Alkynoates, and Tributyltin Methoxide

“…[2] Among the routes to trisubstituted alkenylstannanes, transition-metal-catalyzed stereoselective carbostannylation of internal alkynes with organostannanes is the most straightforward and attractive (Scheme 1a). [3][4][5][6][7] This catalytic method allows the simultaneous formation of CÀC and CÀSn bonds.…”

“…The corresponding amides or ketones as well as nonpolar internal alkynes showed no reactivity as alkyne substrates under similar conditions. Our attempts to use phenyl-9-BBN, PhB(OH) 2 , phenylboronic acid pinacolate ester, or vinylpinacolate ester instead of the alkyl 9-BBN reagents were unsuccessful.…”