Reported herein is the first example of 2-allylazaarenes in asymmetric catalysis. Highly γ-selective allylation was demonstrated for activated ketones, including isatins and trifluoromethyl ketones. In the presence of either an amino-acid-based tertiary amine or quaternary ammonium salt catalyst, two series of tertiary hydroxy-containing moieties were installed at the remote δ-position of azaarenes in good chemical yields, excellent enantioselectivities, and E/Z ratios. The success of current γ-selective reactions should provide inspiration for expansion to other allylazaarene derivatives and would open up new paradigms for the synthesis of chiral γ- and/or δ-functionalized azaarenes.
Science China Chemistry4 scope and up to quantitative yields were achieved at low catalyst loadings with only 5 hydrogen and water as by-products. The protocol was readily extended to the 6 β-alkylation of alcohols with several primary alcohols. Control experiments, along 7 with DFT calculations and crystallographic studies revealed that ligand effect is 8 critical for their excellent catalytic performance, shedding light on more challenging 9 Guerbet reactions with simple alcohols.
Radical addition to olefins is a common and useful chemical transformation. In the context of offering enantioenriched three-dimensional molecules via such a highly reactive process, chiral hydrogen-bonding (H-bonding) catalysis has...
Quaternary α-hydroxyl acids
and their derivatives
have attracted
considerable attention because of their unique and broad functionalities.
Herein, we successfully established a selective and modular protocol
to access quaternary α-hydroxyl acetates via dehydrogenative
cross-coupling of 1,2-diols and primary alcohols by using tris-N-heterocyclic carbene iridium (tris-NHC-Ir, 0.05 mol %)
complexes as catalysts and Ba(OH)2 as the base, along with
the generation of byproducts water and hydrogen gas. A plausible mechanism
involving dehydrogenation of alcohols, aldol-condensation, and 1,2-alkyl
rearrangement reactions was proposed, in which 1,2-alkyl rearrangement
was responsible for the construction of the quaternary carbon center.
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