TiIV-Mediated Reactions between Primary Amines and Secondary Carboxamides: Amidine Formation Versus Transamidation

Titanium(IV)-mediated reactions between primary amines and secondary carboxamides exhibit
different outcomes, amidine formation versus transamidation, depending on the identity of the TiIV complex
used and the reaction conditions employed. The present study probes the origin of this divergent behavior.
We find that stoichiometric TiIV, either Cp*TiIV complexes or Ti(NMe2)4, promotes formation of amidine and
oxotitanium products. Under catalytic conditions, however, the outcome depends on the identity of the TiIV
complex. Competitive amidine formation and transamidation are observed with Cp*TiIV complexes, generally
favoring amidine formation. In contrast, the use of catalytic Ti(NMe2)4 (≤20 mol %) results in highly selective
transamidation. The ability of TiIV to avoid irreversible formation of oxotitanium products under the latter
conditions has important implications for the use of TiIV in catalytic reactions.

钛(IV)催化的伯胺与仲羧酰胺之间的反应呈现出不同的结果，即脒的生成与转酰胺化，这一差异取决于所使用的钛(IV)复合物及其反应条件。本研究旨在探讨这种行为差异的起源。研究发现，等摩尔的钛(IV)复合物，无论是Cp*TiIV复合物还是Ti(NMe2)4，均促进脒及氧钛化合物的生成。然而，在催化条件下，反应的结果则取决于钛(IV)复合物的具体种类。与Cp*TiIV复合物相关的竞争性脒生成与转酰胺化过程，普遍倾向于脒的生成。相比之下，使用催化量的Ti(NMe2)4（≤20 mol %）则导致高度选择的转酰胺化。钛(IV)在上述条件下避免不可逆的氧钛化合物形成的特性，对于钛(IV)在催化反应中的应用具有重要意义。