A new TfOH-mediated reaction of ynamides with nitriles as nucleophiles has been developed. The reaction works efficiently under mild reaction conditions to afford a new class of α-acylaminoenamides readily via the intermediacy of keteniminium ion. The reaction displays generality and a broad substrates scope. Additionally, the α-acylaminoenamides could be transformed to highly substituted pyridine, 4-aminopyrimidine or isoquinoline cores.Download high-res image (152KB)Download full-size image

A fast catalytic synthesis of multisubstituted quinazolines from readily available amidines via visible light-mediated oxidative C(sp3)-C(sp2) bond formation has been established. This reaction is a metal-free oxidative coupling catalyzed by a photoredox organocatalyst. The protocol features low catalyst loading (1 mol %).

A novel one-pot benign oxidative cyclization of alcohols with 2-aminobenzamides was successfully developed without catalyst to afford the quinazolinones under O2. This one-pot protocol involved oxidations and cyclizations to construct the skeleton of quinazolinones through possibly three kinds of distinct reaction mechanisms.

A highly π-facial selective and regioselective fluorination of chiral enamides is described. The reaction involves an enantioselective fluorination exclusively at the electron-rich enamide olefin with N–F reagents such as Selectfluor and N-fluoro-benzenesulfonimide [NFSI] accompanied by trapping of the β-fluoro-iminium cationic intermediate with water. The resulting N,O-hemiacetal could be oxidized using Dess-Martin periodinane, leading to an asymmetric sequence for syntheses of chiral α-fluoro-imides and optically enriched α-fluoro-ketones.

The aerobic oxidation of pyrrolones catalyzed by Fe(OTf)3 to form reactive N-acyliminium ion intermediates that undergo nucleophilic additions with alcohols to give the corresponding products in moderate to good yields is described.

Pyrroloisoquinolines formation through 5-endo halocyclization of unsaturated amides, direct C–H oxidative functionalization and N-acyliminium cyclization is described. A range of β-iodo-pyrrolidinones can be efficiently synthesized using this method, making it an excellent approach for constructing natural products containing pyrrolidinones. Besides, we have developed convenient alternative routes for the synthesis of pyrroloisoquinolines in two separated steps or one pot.

A concise and stereoselective synthesis of the trioxadispiroketal motif that embodies the DEF-ring of the marine macrolide (+)-spirastrellolide A is described. The synthetic approach features a sequence of cyclic acetal tethered ring-closing metathesis and Suárez oxidative cyclization, thereby constituting a viable strategy for constructing the Northern Half.

A concise, stereoselective, and protecting-group-free total synthesis of aplykurodinone-1 from Hajos–Parrish ketone was described. The synthetic approach features a sequence of aerobic allylic oxidation and elimination of alcohol 9. The key intermediate for this synthesis was formed by a stereoselective intramolecular radical cyclization.

Total syntheses of putative (±)-trichodermatides B and C are described. These efficient syntheses feature the oxa-[3+3] annulation strategy, leading to B and C along with their respective C2-epimers. However, these synthetic samples are spectroscopically very different from the natural products. DFT calculations of C13 chemical shifts are conducted and the predicted values are in good agreement with those of synthetic samples, thereby questioning the accuracy of structural assignments of trichodermatides B and C.

The aerobic oxidation of pyrrolones catalyzed by Fe(OTf)3 to form reactive N-acyliminium ion intermediates that undergo nucleophilic additions with alcohols to give the corresponding products in moderate to good yields is described.