Cyclodimerization, acetylene

In the course of research on catalysis by synthetic metalloporphyrins, Tagliatesta and coworkers reported a unique cyclodimerization reaction of aryl acetylenes to give 2-aryl naphthalenes (6, Scheme 9.2) [5]. Ru(CO) and RhCl complexes effectively promote this reaction, with the latter catalyst (8) providing generally superior yields and selectivities for a small range of substrates (Table 9.1). As a synthetic method, Tagliatesta s cyclodimerization reaction is most remarkable for its efficiency. Yields of up to 78% were observed at a substrate/catalyst ratio of 5700 1. Successful recycling of recovered catalyst was also demonstrated. 

Pericyclic reactions involving thiophenes have been utilized to prepare a variety of complex heterocycles. The intramolecular Diels-Alder reaction of 2-vinylbenzo[i]thiophene 92 produced a pair of tetracyclic adducts 93 and 94 <02TL3963>. Coupling of Fischer carbene 96 with 3-alkynylthiophene 95 led to the formation of thieno[2,3-c]pyran-3-one 97 in one step <02JOC4177>. An intramolecular cycloaddition of 97 then afforded tetracyclic adduct 98. A ruthenium-catalyzed cyclodimerization reaction involving bis-thienyl acetylene derivatives was... 

A number of transition metal ion-exchange zeolites are active for acetylene trimerization (159, 160), and the criterion for activity appears to be an even, partially filled d-orbital, i.e., d8 (Ni2 +, Co+), d( (Fe2+), d4 (Cr2 + ). This has led to the suggestion that the mechanism must involve a complex in which there is simultaneous coordination of two acetylene molecules to the transition metal ion. The active oxidation state for CuNaY butadiene cyclodimerization catalysts has been unambiguously defined as monovalent copper (172-180). The d10 electronic configuration of Cu+ is consistent with the fact that isoelectronic complexes of Ni° and Pd° are active homogeneous catalysts for this reaction. The almost quantitative cyclodimerization selec-... 

As well as formation of metallacyclobutenones, reactions of cyclopropenones with transition-metal compounds can lead to acetylene-derived products by decarbonylation, to quinones by a nickel-catalyzed cyclodimerization, and to cluster compounds involving a cleavage of the double bond of the cyclopropenone. ... 

The acetylene was later replaced by butadiene for economic reasons. Butadiene is cyclodimerized, then hydrogenated to cyclooctane, and the oxime is prepared directly from cyclooctane by photonitrosation ... 

As illustrated in the early achievements from Reppe on the cyclotetramerization of acetylene and from Wilke on the cyclodimerization and cyclotrimerization of butadienes, nickel-catalyzed cycloadditions possess considerable potential in the construction of medium ring systems. Pioneering studies by Wender have demonstrated many practical implications that have advanced the... 

Copper(i) triflate is an excellent catalyst for the photochemical cyclodimerization of cyclopentene. Irradiation of the annelated cyclopentene (336) with olefins and acetylenes provides a useful route to propellanes such as (337). ... 

The nickel(O) complex Ni4(CNBu07 catalyzes reduction of acetylenes to olefins, isocyanides and cyanides to amines, as well as cyclotrimerization of acetylene and cyclodimerization of butadiene. Reduction of isocyanides is also catalyzed by other clusters (Chapter 13). Isocyanide copper compounds catalyze addition of CH2CIY (Y = COOR, COR, CN) to olefins leading to the formation of cyclopropane derivatives... 

The widely known Repp s synthesis of cyclo-octatetraene by tetra-merization of acetylene undoubtedly involves a metal jt-complex intermediate. However, a clear-cut mechanism for this reaction has not yet been advanced. The formation of a cyclobutadiene ring by cyclodimerization of... 

Postulate mechanisms for the cyclodimerization, trimerization, and tetramerization of acetylenes. 

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