HOO• as the Chain Carrier for the Autocatalytic Photooxidation of Benzylic Alcohols.

The oxidation of benzylic alcohols is an important transformation in modern organic synthesis. A plethora of photoredox protocols have been developed to achieve the aerobic oxidation of alcohols into carbonyls. Recently, several groups described that ultraviolet (UV) or purple light can initiate the aerobic oxidation of benzylic alcohols in the absence of an external catalyst, and depicted different mechanisms involving the photoinduction of •O2- as a critical reactive oxygen species (ROS). However, based on comprehensive mechanistic investigations, including control experiments, radical quenching experiments, EPR studies, UV-vis spectroscopy, kinetics studies, and density functional theory calculations (DFT), we elucidate here that HOO•, which is released via the H2O2 elimination of α-hydroxyl peroxyl radicals [ArCR(OH)OO•], serves as the real chain carrier for the autocatalytic photooxidation of benzylic alcohols. The mechanistic ambiguities depicted in the precedent literature are clarified, in terms of the crucial ROS and its evolution, the rate-limiting step, and the primary radical cascade. This work highlights the necessity of stricter mechanistic analyses on UV-driven oxidative reactions that involve aldehydes' (or ketones) generation.

One-Pot Synthesis of Indolin-3-ones Mediated by LiN(SiMe3)2/CsF.

Indolin-3-ones are essential heterocycles with wide-ranging biological activities and medicinal values, and therefore, efficient approaches to their synthesis remain in demand. Herein, a novel and operationally simple method to generate indolin-3-ones is reported by using a tandem reaction of N-methylbenzylamines and methyl 2-fluorobenzoates mediated by the LiN(SiMe3)2 and CsF system (34 examples, 30-85% yields). The synthesis of C2-quaternary indolin-3-one further demonstrated the potential practicability of these tandem reactions.

Base-Promoted Synthesis of Isoquinolines through a Tandem Reaction of 2-Methyl-arylaldehydes and Nitriles.

A convenient method for preparing 3-aryl isoquinolines via a base-promoted tandem reaction is presented. Simply combining commercially available 2-methyl-arylaldehydes, benzonitriles, NaN(SiMe3)2, and Cs2CO3 enabled the synthesis of a variety of isoquinolines (23 examples, ≤90% yield). Among the syntheses of isoquinolines, the transition metal-free method described here is straightforward, practical, and operationally simple.

Synthesis of Homoallylamines Enabled by Cobalt or Palladium Catalyzed Allylic Substitution of Azaarylmethylamines.

Pd(OAc)2/Nixantphos or CoI2/Nixantphos catalyzed allylic substitutions with weakly acidic C(sp)3-H bonds of azaarylmethylamines are described. This method facilitates access to various kinds of heteroaryl rings containing homoallylamines (39 examples, 30-98% yields) with excellent functional group tolerance and diastereoselectivity. Compared with the Pd/Nixantphos complex, the Co/Nixantphos catalysis could obtain the cyclic products with good to excellent diastereoselectivities. Importantly, the CoI2/(R,R)-Me-Duphos catalyzed reactions exhibit moderate enantioselectivity. Additionally, the scalability of this transformation is successfully demonstrated.