A Highly Enantioselective Catalyst for the Asymmetric Nozaki–Hiyama–Kishi Reaction of Allylic and Vinylic Halides

Abstract

Catalytic asymmetric addition of vinylic halides and triflates to aldehydes, with useful levels of stereoinduction, has been achieved for the first time using the salen‐type ligand (S,S)‐5 (see scheme; PMB=para‐methoxybenzyl), which contains the novel endo,endo‐2,5‐diamino norbornane building block. This asymmetric Nozaki–Hiyama–Kishi reaction leads to the coupling of various halides and aldehydes with high yields and enantioselectivities (up to 92 % ee).

Extremely Active Organocatalysts Enable a Highly Enantioselective Addition of Allyltrimethylsilane to Aldehydes

“…[4] Af ew years later,B rown et al introduced B-allyldiisopinocampheylborane,w hich has been the most popular chiral allylating agent until today. [3] To this end, several effective catalytic variants with achiral allylboron reagents, [9,10] allylstannanes, [11][12][13] allyl halides, [14,15] and allyl acetates [16] have been developed. [3] To this end, several effective catalytic variants with achiral allylboron reagents, [9,10] allylstannanes, [11][12][13] allyl halides, [14,15] and allyl acetates [16] have been developed.…”

“…[5] Such chiral reagents [6][7][8] have proven to be of considerable synthetic value,although the intrinsic need for wasteful stoichiometric, and usually non-recoverable amounts of enantiopure auxiliaries affect atom economy,c ost, environmental impact, and the overall synthetic appeal of the methodology. [3] To this end, several effective catalytic variants with achiral allylboron reagents, [9,10] allylstannanes, [11][12][13] allyl halides, [14,15] and allyl acetates [16] have been developed. Nevertheless,t he nonnegligible high toxicity of stannanes and chromium complexes [14,15] significantly restricted the broad application of some of these methods.A lternatives,s uch as the multicomponent catalyst systems employing iridium complexes, [16] require high temperature and al arge excess of reagents.…”

“…[3] To this end, several effective catalytic variants with achiral allylboron reagents, [9,10] allylstannanes, [11][12][13] allyl halides, [14,15] and allyl acetates [16] have been developed. Nevertheless,t he nonnegligible high toxicity of stannanes and chromium complexes [14,15] significantly restricted the broad application of some of these methods.A lternatives,s uch as the multicomponent catalyst systems employing iridium complexes, [16] require high temperature and al arge excess of reagents. Comparatively,a llylsilanes are considered nontoxic,a ir-a nd moisture-stable,o ften commercially available,a nd easily prepared and handled.…”

Synthesis of chromium(III) bis(benzamidinate) complexes via single electron oxidation

“…As previously noted in other systems, addition of electron donating ligands with N donor atoms increases the rate at which Cr(II) reacts with organic substrates in one-electron oxidative addition reactions [4,40]. In this case, complex 1 reacts in pentane with allylic esters, a class of reactants outside of the scope typically employed in organic synthetic applications of CrCl 2 , where allyl bromides and chlorides are normally used [7,[10][11][12][13][14][15], although use of allyl tosylates and mesylates have also been reported [7].…”

“…In 1996, Fürstner and co-workers rendered the reaction catalytic in chromium, using Me 3 SiCl to break the inert Cr(III)-oxygen bond, and Mn as the stoichiometric reductant to regenerate the active Cr(II) species [9]. In the decade since Fürstner's report of the catalytic reaction, several groups have reported chiral ligand systems to render the coupling of allyl halides and aldehydes catalytic and enantioselective [8,[10][11][12][13][14][15][16].…”