Fe-Catalyzed Difunctionalization of Aryl Titanates Enabled by Fe/Ti Synergism

Abstract

Fe-catalyzed difunctionalization of aryl titanates via double C–H activation has been developed, where aryl titanates were arylated via ortho C–H activation, followed by ipso electrophilic trapping of the C–Ti bond. The ortho C–H arylation should be promoted by a 1,2-Fe/Ti synergistic heterobimetallic arylene intermediate and represents an ortho C–H ferration directed by a readily transformable C–Ti group. Common benzamides, esters, and nitriles function as arylating reagents, which involves another ortho C–H activation directed by these functionalities.

Modular and Regioselective Synthesis of Benzo-Fused Five-Membered Rings Enabled by Co/Ti Synergism

“…cause the cyclization to occur ortho to them (between the substituents and the C–Ti bond, 4g , 4h , also see 4o - r ; 5f – h ; 6c – d ; 8 and 9c – d ). Such regioselectivity should originate from the cobaltation to form Co/Ti arylene bimetallic intermediates ( 2a in Table ), which is similar to the ferration that we have previously reported . Compared with the existing indole synthesis method, this regioselectivity model has obvious advantages because it provides a convenient method for accessing synthetically challenging 4-substituted indoles .…”

“…Recently, we have obtained ortho Fe/Ti arylene complexes by Fe/Ti synergism and developed a regioselective ortho difunctionalization of arenes . Inspired by this bimetallic synergism, we envision that an ortho Co/Ti arylene intermediate can also be regioselectively formed by Co/Ti synergism (Scheme B), whose Co can add across alkynes to generate a benzotitanole; and various benzo-fused five-membered heterocycles or indenones can be accessed through late-stage introduction of heteroatoms or CO by reacting the benzotitanole with EX 2 (E = NR, S(O), RP(O), R 2 Si, CO, etc.).…”

Modern Organometallic C−H Functionalizations with Earth‐Abundant Iron Catalysts: An Update

“…Shortly after, the same research group reported a catalytic version of the ortho difunctionalization (ODF) of arenes via Fe/Ti-heterobimetallic arylene intermediate (Scheme 19). [55] Here, the aryl titanate 37 [56] is submitted to the arylating reagent (38) with just a catalytic amount of the iron catalyst and ligand (FeCl 2 and TMEDA respectively).1,2-DCE is used as an oxidant to achieve the ortho CÀ H arylation of 38 at the Fe site, followed by a reaction with CO 2 as the electrophile at the Ti site. The optimized catalytic system was applied to the ODF of various aryl titanates, bearing an alkyl or aryl group at 2-position, with a family of differently substituted arene partners.…”