Recent developments in enantioselective zinc-catalyzed transformations

Abstract

This review collects the recent advances in the field of enantioselective zinc-catalyzed transformations, covering the literature since the beginning of 2015, illustrating the power of chiral green zinc catalysts to promote all types of reactions. A range of highly enantioselective reactions have been developed in the last six years, including cycloadditions, alkynylation/allylation reactions of carbonyl compounds and derivatives, additions of diorganozincs to carbonyl compounds and derivatives, Mannich reactions, (nitro)aldol reactions, other 1,2-nucleophilic additions to carbonyl compounds and derivatives, Michael additions, Friedel-Crafts reactions, reductions, a-functionalizations of carbonyl compounds, ringopening reactions, epoxidations, halolactonizations, domino/tandem reactions and miscellaneous reactions.

Reactions of Zinc Hydride with Silylenes: From Oxidative Addition to Ligand Exchange Reactions

“…Found: C, 75.3; H, 8.79; N, 5.81. 1 H NMR (600 MHz, THFd 8 , 25 °C) δ = 0.13 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 0.16 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 0.24 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 0.44 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 0.86 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 0.87 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 0.91 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 0.98 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 1.07 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.09 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.16 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 1.17 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 1.28 (d,…”

“…T he synthesis of donor−acceptor complexes of diorganozinc compounds with N-heterocyclic carbenes has been intensively studied in recent years due to their promising technical applications in organic catalysis, 1−3 whereas comparable reactions with heavier silylenes are still scarce. Nheterocyclic silylene L 1 Si was reported to react with ZnMe 2 with oxidative addition to the bis-silyl complex [L 1 (Me)Si] 2 Zn (L 1 = ArNC(CH 2 )CHC(Me)NAr, Ar = 2,6-iPr 2 C 6 H 3 ) (Scheme 1), 4 whereas the chloro-substituted silylene L 2 SiCl (L 2 = PhC(NtBu) 2 ) reacted with ZnR 2 (R = C 5 Me 5 , Ph, Et) with R/Cl ligand exchange and formation of L 2 Si(R)−Zn(R) Cl and [L 2 Si(R)] 2 ZnCl 2 , respectively (Scheme 1). 5 In contrast, Cp*-substituted silylene L 2 SiCp* (Cp* = C 5 Me 5 ) was reported to react with zinc dihalides ZnX 2 to halide-bridged dimers [{PhC(NtBu) 2 }(C 5 Me 5 )SiZnX(μ-X)] 2 and with several ZnR 2 (R = Ph, Et, C 6 F 5 ) to the corresponding monomeric complexes [{PhC(NtBu) 2 }(C 5 Me 5 )SiZnR 2 ] (Scheme 1).…”

“…Melting point: 230 °C (dec.). 1 H NMR (400 MHz, benzene-d 6 , 25 °C) δ = 0.69 (s, 18H, tBu), 1.20 (d, 3 J HH = 6.8 Hz, 12H, CHMe 2 ), 1.38 (d, 3 J HH = 6.8 Hz, 12H, CHMe 2 ), 1.64 (s, 6H, CMe), 2.73 (s, 6H, NMe 2 ), 3.27 (sept, 3 J HH = 6.7 Hz, 4H, CHMe 2 ), 5.02 (s, 1H, CH), 5.21 (s, 1H, PhCH), 6.76−7.17 (m, 11H, C 6 H 5 and C 6 H 3 ); 13 C{ 1 H} NMR (100 MHz, benzene-d 6 , 25 °C) δ = 24.6 (CHMe 2 ), 24.8 (CMe), 28.9 (CHMe 2 ), 31.9 (tBu), 38.2 (NMe 2 ), 49 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 0.20 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 0.25 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 0.79 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 0.88 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 0.94 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 0.97 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.06 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.10 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.18 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.20 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.28 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 1.31 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.40 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.42 (d, 3 J HH = 6.0 Hz, 3H, CHMe 2 ), 1.61 (d, 3 J HH = 12.0 Hz, 3H, CHMe 2 ), 1.71 (s, 3H, CMe), 1.82 (s, 3H, CMe), 1.89 (s, 3H, CMe), 1.91 (s, 3H, CMe), 2.30 (sept, 3 J HH = 12.0 Hz, 1H, CHMe 2 ), 2.39 (sept, 3 J HH = 12.0 Hz, 1H, CHMe 2 ), 2.55 (sept, 3 J HH = 12.0 Hz, 1H, CHMe 2 ), 2.87 (sept, 3 J HH = 12.0 Hz, 1H, CHMe 2 ), 2.96 (sept, 3 J HH = 12.0 Hz, 1H, CHMe 2 ), 3.12 (m, 2H, CHMe 2 ), 3.70 (sept, 3 Single-Crystal X-ray Diffraction of 1−6. Suitable crystals of 1− 6 were selected and mounted on a suitable support under inert oil on a Bruker D8 Venture with Photon 2 detector (monochromated CuKα radiation, λ = 1.54178 Å, microfocus source; 1, 2) and a Bruker APEX-II CCD diffractometer (monochromated MoKα radiation, λ = 0.71073 Å; 3), respectively, at low temperature (T = 100(2) K).…”

“…The synthesis of donor–acceptor complexes of diorganozinc compounds with N-heterocyclic carbenes has been intensively studied in recent years due to their promising technical applications in organic catalysis, − whereas comparable reactions with heavier silylenes are still scarce. N-heterocyclic silylene L 1 Si was reported to react with ZnMe 2 with oxidative addition to the bis-silyl complex [L 1 (Me)­Si] 2 Zn (L 1 = ArNC­(CH 2 )­CHC­(Me)­NAr, Ar = 2,6- i Pr 2 C 6 H 3 ) (Scheme ), whereas the chloro-substituted silylene L 2 SiCl (L 2 = PhC­(N t Bu) 2 ) reacted with ZnR 2 (R = C 5 Me 5 , Ph, Et) with R/Cl ligand exchange and formation of L 2 Si­(R)–Zn­(R)Cl and [L 2 Si­(R)] 2 ZnCl 2 , respectively (Scheme ).…”

Factors controlling the structure of alkylzinc amidinates: on the role ofN-substituents

“…Heteroleptic alkylzinc compounds are of longstanding interest due to their important role in various stoichiometric and catalytic chemical processes [1][2][3][4][5][6][7] and more recently as efficient predesign precursors of modern functional materials. [8][9][10][11] However, the characterization of organozinc reactants and intermediate states is often challenging as they commonly exhibit complicated behavior in solutions involving multiple equilibria between various aggregated forms and non-stoichiometric species arising from Schlenk equilibria.…”