Functionalized mercaptoacetic and propionic acid amides: synthesis, cyclopalladation features, and catalytic activity of metal complexes

Design of pincer complexes based on (methylsulfanyl)acetic/propionic acid amides with ancillary S‐ and N‐donors as potential catalysts and cytotoxic agents

“…Thus, the lowest catalytic activity among the complexes obtained was observed for quinoline‐containing derivatives 11 and 11o , which provided only 42 and 26% conversion of 4‐bromoacetophenone at a relatively high (pre)catalyst concentration – 1 mol% (Table , entries 5, 11, 17 and 23). These results are in good agreement with the data obtained for related quinoline‐based complexes having different S‐coordination arms (Figure S28 in supporting information), which in general demonstrated low efficiency in the Suzuki cross‐coupling, with palladocycles having the most rigid ligand framework being the least active. As for S,N,S‐complexes 12 and 12o , only the sulfide‐based derivative displayed a reasonable level of activity in the coupling of 4‐bromoacetophenone (Table , entries 6, 12, 18 and 24).…”

“…As for S,N,S‐complexes 12 and 12o , only the sulfide‐based derivative displayed a reasonable level of activity in the coupling of 4‐bromoacetophenone (Table , entries 6, 12, 18 and 24). Although other S,N,S‐complexes derived from 2‐diphenylthiophosphorylaniline appeared to be more active towards this substrate (Figure S29 in supporting information), almost all of them were inefficient in reactions with 4‐bromoanisole. As we anticipated, the N,N,S‐complexes with aminoalkylpyridine pendant arms featuring more flexible ligand backbone displayed much more marked catalytic performance.…”

“…The degree of ligand framework flexibility and the nature of ancillary donor groups determine the ease and rate of generation of these catalytically active species. Similar mechanistic outcomes and structure–activity dependences were observed earlier for the N,N,S‐complexes derived from phenylsulfanylacetic acid and 2‐methylsulfanylbenzoic acid . However, the introduction of methyl substituent at the sulfur atom instead of phenyl one facilitated the improvement of catalytic performance of this type of metal complex (Figure ).…”

“…The catalytic activity of the cyclopalladated complexes obtained was tested in the convenient model Suzuki cross‐coupling of aryl bromides with PhB(OH) 2 . For correct comparison of the results, all the experiments were carried out under the conditions used previously for the related Pd(II) pincer complexes based on functionalized carboxamides[4c,9]: heating in dimethylformamide (DMF) at 120 °C for 5 h using K 3 PO 4 as a base (Scheme ). Owing to strongly differing electronic properties of para ‐substituents, two aryl bromides (4‐bromoacetophenone and 4‐bromoanisole) served as two extreme points for elucidation of structure–activity relationships.…”

“…In recent years, our research group has extended a range of pincer‐type palladocycles based on functionalized carboxamides with several series of complexes (see, for example, Scheme ) [3c,d,4c,7a,8,9]. Some of them demonstrated pronounced cytotoxic effects against human colon (HCT116), breast (MCF7) and prostate (PC3) cancer cells (compounds XII and XIII );[7a,8] others exhibited moderate to high catalytic activity in Suzuki cross‐coupling (compounds XIV – XVI ) . The performed investigations allowed us to outline preliminary tendencies in the structure–activity relationships.…”