A silica-supported titanium catalyst for heterogeneous hydroamination and multicomponent coupling reactions

Abstract

A highly dehydrated silica gel, when exposed to Ti(NMe2)4, gives a fast, high-yielding catalyst for multicomponent coupling of an amine, alkyne, and isonitrile to form 1,3-dimine tautomers, iminoamination.

Readily available Ti-based in situ catalytic system for oxo/imido heterometathesis

“…Noteworthily, Odom has already demonstrated the application of the supported Ti amides for hydroamination and iminoamination reactions where the amine serves as one of the reactants. 46,47 In this report, we show that commercially available Ti(NEt 2 ) 4 grafted on a silica surface can be used as a very efficient oxo/imido heterometathesis pre-catalyst with the activity on the same scale as the most active well-defined supported Ti imides.…”

“…Grafting of Ti tetraamides on silica has been studied by many groups. [46][47][48][49][50][51][52] In agreement with these works, we found that treatment of SiO 2-700 (silica dehydroxylated at 700 °C) with a solution of Ti(NEt 2 ) 4 gave a yellow material 1 containing 0.22 ± 0.03 mmol Ti per g (consistent with quantitative grafting, the absence of unreacted Ti(NEt 2 ) 4 in NMR of washings, and full consumption of the uSiOH IR band of silica (Fig. S2, ESI †)) along with the liberation of ca.…”

Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

“…The final MCR adduct precipitated in the reaction medium and remained adsorbed in the heterogeneous catalysis, whereas in the homogeneous version, product separation was far less laborious. Some multicomponent syntheses, however, may be efficiently conducted under heterogeneous conditions with effective catalytic system recovery [ 196 , 197 , 198 , 199 , 200 , 201 ]. Metal–organic frameworks (MOFs) are, however, active, programmable and recyclable catalysts successfully applied in MCR syntheses, as recently reviewed elsewhere [ 202 , 203 , 204 ].…”

Efficient Hydroboration of Esters and Nitriles Using a Quinazolinone‐Supported Titanium(IV) Multitasking Catalyst

“…[18] However, the oxophillic and moisture-sensitive nature of titanium complexes limits its potential use as a catalyst for the synthesis of fine chemicals, pharmaceuticals, and agrochemicals in comparison to late transition metal catalysts. [19] Over the last two decades, titanium-catalyzed hydroamination [20] and hydroalkylamination [21] have been established as reliable transformation tools to develop a diverse array of chemical compounds such as substituted amines, N-heterocycles, alcohols, etc. [22,23] Hydroboration of nitriles and esters is more challenging due to the presence of stable C=O and C�N polar bonds compared to the non-polar unsaturated bonds.…”