Regio- and enantioselective formation of tetrazole-bearing quaternary stereocenters via palladium-catalyzed allylic amination

Based on palladium-catalyzed allylic amination reaction, the first general example of enantioselective formation of tetrazole-bearing quaternary stereocenter has been developed. The protocol utilizes ambivalent tetrazole and vinyl cyclic carbonates as...

Organophotoredox/Ni-Cocatalyzed Allylation of Allenes: Regio-, and Diastereoselective Access to Homoallylic Alcohols

A dual organophotoredox/nickel-catalyzed reductive coupling of allenes with aldehydes has been developed for the rapid assembly of anti-homoallylic alcohols with high levels of regioselectivities (>20:1), and diastereoselectivities (up to >20:1) and yields (up to 91%). The allylation was realized through a crucial π-allylnickel intermediate which was obtained via insertion of allenes with a Ni−H intermediate. Moreover, γ,γ-disubstituted homoallylic alcohols with a quaternary stereocenter can also be prepared by this protocol.

Divergent Synthesis of Indolenine and Indoline Ring Systems by Palladium-Catalyzed Asymmetric Dearomatization of Indoles

Dearomatized indole derivatives bearing a C3- or C2-stereocenter exist ubiquitously in natural products and biologically active molecules. Despite remarkable advances in their chemical synthesis, stereoselective and regio-divergent methods are still in a high demand. Herein, a Pd-catalyzed intermolecular asymmetric spiroannulation of 2,3-disubstituted indoles with internal alkynes has been developed for the efficient construction of indoline structures with a C2-quaternary stereocenter. Stereospecific aza-semipinacol rearrangement of these indoline derivatives under acidic conditions afforded indolenine products bearing a C3-quaternary stereocenter, where the selectivity for the rearranging group could be controlled by the reaction sequence. The asymmetric spiroannulation together with the subsequent aza-semipinacol rearrangement enabled a divergent access to dearomatized indole derivatives with either a C3- or a C2-quaternary stereocenter.

A concise access to bridged [2,2,1] bicyclic lactones with a quaternary stereocenter via stereospecific hydroformylation

Chiral bridged [2,2,1] bicyclic lactones are privileged structural units in pharmaceutics and bioactive nature products. However, the synthetic methods for these compounds are rare. Here we report an efficient method for enantioselective construction of bridged [2,2,1] bicyclic lactones bearing a quaternary stereocenter via Rh-catalyzed asymmetric hydroformylation/intramolecular cyclization/pyridium chlorochromate (PCC) oxidation. By employing a hybrid phosphine-phosphite chiral ligand, a series of cyclopent-3-en-1-ols are transformed into corresponding γ-hydroxyl aldehydes with specific syn-selectivity. Then, hemiacetals form in situ and oxidation with PCC in one-pot affords bridged [2,2,1] bicyclic lactones in high yields and excellent enantiomeric excess. Replacing the hydroxyl group by an ester group, cyclopentanecarbaldehydes with a chiral all-carbon quaternary stereocenter in the γ-position can be generated efficiently.