Ring closing metathesis employing organometallic substrates and the templated synthesis of macrocycles

Abstract

Templation is a well-known strategy for the selective generation of complex products. Ring-closing metathesis, catalyzed by well-characterized Ru and Mo catalysts, is a powerful method for C C bond formation and has certainly developed into one of the most important modern reactions in organic synthesis and in polymer chemistry. Despite the extensive research on this reaction, the use of organometallic containing substrates is not well-studied. Here, we give a detailed account of our ongoing efforts to employ ring-closing metathesis with bis(␣-olefin) substituted pyridines in the presence of trimeric metallopincer templates for the selective synthesis of macroheterocycles with ring sizes up to 81 atoms.

Entropy-driven ring-opening olefin metathesis polymerizations of macrocycles

“…In the other report, the authors prepared 23-membered pyridinocyclophanes 15 and 16 in less than 10 min, and in quantitative yield, via RCM initiated with 5 mol% 1 under dilute conditions (1 mM). 54 However, upon concentration of the desired RCM products, in the presence of remaining 1, an intractable polymeric solid was obtained. These documented observations underscore the ease of dynamic ED-ROMP of macrocyclic would-be products if concentrated in the presence of active metathesis catalysts.…”

Merging Porphyrins with Organometallics: Synthesis and Applications

“…Later, the authors found that heteromultimetallic complexes [186] could be obtained by selecting the right order of metalation steps of the parent multitopic ligands. These pincer-porphyrin hybrids were subsequently used as templates in ring-closing metathesis, [187] as catalysts, [188] and as catalyst precursors. [189] For example, a series of tetrakis(SCS-PdCl)-metalloporphyrin hybrids was synthesized by two distinct synthetic routes: 161 MnCl and 161 Ni were synthesized by fourfold electrophilic palladation of the corresponding tetrakis(SCS)-metalloporphyrins with [Pd(NCMe) 4 ]-(BF 4 ) 2 in MeCN/CH 2 Cl 2 in yields of circa 90 %, whereas 161 Mg was obtained by treatment of 161 with MgBr 2 •OEt 2 .…”

Erasable Coordination Polymer Multilayers on Gold

“…We utilize Pd II pincer-type complexes [15] because of their association strength [16] and inertness toward a variety of functionalities, [14c] including polar, nonpolar, charged, and even acidic groups. Furthermore, Pd II pincer complexes are tolerant toward many reaction conditions, including organometallic reactions, [17] yet responsive toward stronger coordinating ligands. In our study, the Pd II pincer complexes are supported on poly(norbornene) derivatives, PNBE + (M w = 30 000).…”