Intermolecular Alkyne Hydroaminations Involving 1,1-Disubstituted Hydrazines

Abstract

[reaction: see text] Two readily prepared catalysts have been developed for the hydroamination of alkynes by 1,1-disubstituted hydrazines. The catalyses are facile with terminal alkynes and some internal alkynes. If the hydrazine bears an aryl group, Fischer cyclization can occur in a one-pot procedure. In addition, reactions with acetylene to produce a plethora of hydrazones are described. Catalytic reactions involving acetylene and substituted hydrazines are complete in less than 2 h at room temperature and 1 atm of pressure.

Transition‐Metal‐Catalyzed Hydroamination Reactions

“…Approaches for indole synthesis using hydroamination as a key step in their syntheses has been an ongoing area of investigation over the past several years [329,330]. Early examples focused on one-pot intermolecular hydrohydrazination followed by the Lewis-acid-catalyzed Fischer indole synthesis [331,332] (Scheme 15.102) or one-pot intermolecular hydroamination followed by cross-coupling to either form a C-N bond (via the Buchwald-Hartwig amination) [333] (Scheme 15.103) or a C-C bond (via a Heck reaction) [334,335] (Scheme 15.104).…”

Modular N,O‐Chelating Ligands: Group‐4 Amidate Complexes for Catalytic Hydroamination

“…[65][66][67][68] Following an initial report of titanium catalyzed hydroamination by Rothwell and coworkers, [69] research into hydroamination catalysis has also followed the trend of focusing on Cp-based ligand systems and then moving onto non-Cp-based catalysts. A variety of systems have been developed for hydroamination reactions including work from the groups of Bergman, [15,64,[70][71][72][73] Livinghouse, [74,75] Odom, [67,[76][77][78][79][80][81] Beller, [65,[82][83][84][85][86] Doye, [87][88][89][90][91][92][93][94] ourselves, [59,61,62,95,96] and others. [11,[97][98][99][100][101][102][103][104]…”

Titanium-catalyzed iminohydrazination of alkynes

“…Using titanium catalysts, alkynes can be hydrohydrazinated [4] (Scheme 2) with 1,1-disubstituted hydrazines, a process that generates hydrazones and indoles (after Fischer cyclization) [5,6]. This procedure recently has been elegantly expanded by Ackermann [7] and Beller [8] using alternative titanium catalysts to generate a variety of indole derivatives.…”