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Chiral phosphoric acid-catalyzed asymmetric aldehyde prenylation has been established using an α,α-dimethyl allyl boronic ester. The transformation provides expedient access to a wide array of aryl, heteroaryl, aryl-substituted alkenyl and primary and secondary aliphatic homoprenyl alcohols with excellent asymmetric induction. The utility of this asymmetric catalysis strategy has been demonstrated through a short and efficient total synthesis of the two natural products (−)-rosiridol and (−)-bifurcadiol. [ABSTRACT FROM AUTHOR]

Boron‐reagents are very useful tools in synthetic organic chemistry and have been extensively explored in the asymmetric methodology development. The past decade has witnessed an upsurge of interest in exploring their application in the asymmetric total synthesis. Several synthetic strategies, such as the transmetalation strategy, the boronate ligand exchange strategy, the Lewis base and Brønsted acid activation strategies, and the lithiation‐borylation strategy, offered very powerful platforms for the development of innovative synthetic routes for asymmetric total synthesis. This review highlights the progress (2007–2019) of the application of these synthetic strategies in the asymmetric total synthesis of natural products, and of biologically and medicinally relevant molecules. [ABSTRACT FROM AUTHOR]

A CuII‐catalyzed asymmetric 1,3‐dipolar cycloaddition using β‐fluoroalkyl alkenyl arylsulfones as dipolarophiles and glycine/alanine iminoesters as azomethine ylide precursors has been developed. Remarkably, a catalyst loading as low as 0.5 mol % is highly efficient. Accordingly, a wide range of enantioenriched 3‐fluoroalkyl pyrrolidines, as well as Δ2‐pyrroline and pyrrole derivatives, are generated in good to excellent yields with high asymmetric induction. This synthetic approach is diastereodivergent in that exo‐adducts could be converted into the corresponding exo′‐adducts by 1,8‐diazabicyclo[5.4.0]undec‐7‐ene mediated epimerization at C2 of the pyrrolidine core. The free‐energy profiles from DFT calculations suggest the Michael addition of the 1,3‐dipole to be the rate‐ and enantiodetermining step, and the origin of stereoselectivity is studied by means of the noncovalent interaction (NCI) analysis. [ABSTRACT FROM AUTHOR]

In this report, we presented a new approach to access a (1,3-butadiene-2-yl)carbinol, (1R,2R)- and (1S,2S)-1-(hydroxymethyl)-1-vinyl-1,2,3,4-tetrahydronaphthalene-2-ols. Starting from commercially available 1,4-diol-2-butyne, a six-step synthesis involving dibromination, Zn-mediated addition reaction of phenylpropyl aldehyde, epoxidation, epoxy-arene cyclization, and resolution with D(+)-Camphor afforded the title compounds. [ABSTRACT FROM AUTHOR]

2-Pyridylsulfone- and fluoroalkylated group-activated olefins underwent highly efficient diastereo- and enantioselective 1,3-dipolar cycloadditions across various aromatic and aliphatic nitrones in the presence of a chiral NiII/bis(oxazoline) catalyst. The process was tuned by 4 Å molecular sieves, chiral bis(oxazoline) ligands, reaction solvents, and temperature. A wide array of optically pure fluoroalkylated isoxazolidines were obtained, thus facilitating the asymmetric synthesis of an enantioenriched α-trifluoromethylated γ-amino alcohol in gram-scale and a trifluoromethylated derivative of 1,3-oxazinan-2-one with potential pharmaceutical interest. A stereochemical model, based on the absolute configuration of one adduct and some control experiments, was postulated to account for the observed endo- and enantioselectivity. [ABSTRACT FROM AUTHOR]

Given the important agricultural and medicinal application of optically pure heterocycles bearing a trifluoromethyl group at the stereogenic carbon center in the heterocyclic framework, the exploration of efficient and practical synthetic strategies to such types of molecules remains highly desirable. Catalytic enantioselective synthesis has one clear advantage that it is more cost-effective than other synthetic methods, but remains limited by challenges in achieving excellent yield and stereoselectivities with a low catalyst loading. Thus far, numerous models of organo- and organometal-catalyzed asymmetric reactions have been exploited to achieve this elusive goal over the past decade. This review article describes recent progress on this research topic, and focuses on an understanding of the catalytic asymmetric protocols exemplified in the catalytic enantioselective synthesis of a wide range of complex enantioenriched trifluoromethylated heterocycles. [ABSTRACT FROM AUTHOR]

Abstract: A new class of dendritic monodentate phosphoramidite ligands were synthesized through substitution of the dimethylamino moiety in MonoPhos by the Fréchet-type dendritic wedge and applied in the asymmetric hydrogenation of α-dehydroamino acid esters and dimethyl itaconate. High enantioselectivities (up to 97.9% ee) and catalytic activities (up to 4850h−1 TOF) were achieved, which are better or comparable to those obtained from MonoPhos. The third generation dendrimer catalyst gave the slightly lower catalytic activity relative to the lower generation ones. The steric shielding by the dendrimer could stabilize the rhodium complex against decomposition caused by hydrolysis in a protic solvent. The inactive catalysts (RhL3 and RhL4) were activated by addition of a free metal precursor Rh(COD)2BF4, and showed high enantioselectivities and catalytic activities. [Copyright &y& Elsevier]

A new kind of functionalized Janus dendrimer has been synthesized via a liquid-phase approach, which could easily be purified using a simple precipitation method without the need for chromatographic separation. Their use for liquid-phase organic synthesis has been achieved in the Pd-catalyzed Suzuki coupling reactions, giving biaryl products in excellent yields after cleavage. [ABSTRACT FROM AUTHOR]