Cyclo-oligomerization

The cyclooligomerization of ethylene oxide to yield dioxane as well as compounds we now call crowns predates Pedersen s discovery by more than a decade ". The full utility of these cyclic oligomers was not recognized, however, and the patent reporting these early efforts remains an interesting historical footnote. The promise of utilizing cyclo-oligomerization commercially is so important, however, that attention is called to the method and the existence of the patent. 

A small number of template mediated reactions which afford thioether macrocycles are also known, e.g. the small trithia [9]aneS3 is also obtained in good yield using Mo(CO)3 as a template.73,74 The crown trithioether is readily demetallated by addition of a further equivalent of [NMe4]2[S(CH2)2S(CH2)2S]. Also, dibenzo-[18]aneS6 and dibenzo-[15]aneS5 have been prepared via an iron dicarbonyl template.75,76 Metal-induced cyclo-oligomerization reactions of... 

Structure-Reactivity Relationships in the Cyclo-Oligomerization of 1,3-Butadiene Catalyzed by Zerovalent Nickel Complexes... 

The catalytic cyclo-oligomerization of 1,3-butadiene mediated by transition-metal complexes is one of the key reactions in homogeneous catalysis.1 Several transition metal complexes and Ziegler-Natta catalyst systems have been established that actively catalyze the stereoselective cyclooligomerization of 1,3-dienes.2 Nickel complexes, in particular, have been demonstrated to be the most versatile catalysts.3... 

The catalytic cyclo-oligomerization of 1,3-butadiene was first reported by Reed in 1954 using modified Reppe catalysts.4 Wilke et al., however, demonstrated in pioneering, comprehensive and systematic mechanistic investigations, the implications, versatility and the scope of the nickel-catalyzed 1,3-diene cyclo-oligomerization reactions.3,5... 

Although the pioneering, systematic, and comprehensive experimental work of Wilke et al3,5 has led to a thorough understanding of the nickel-catalyzed cyclo-oligomerization reaction of 1,3-butadiene, there are still some essential mechanistic details that are not yet firmly established (vide infra). In the following account, we summarize recent progress in the... 

CATALYTIC REACTION CYCLES FOR THE NICKEL-CATALYZED CYCLO-OLIGOMERIZATION OF 1,3-BUTADIENE... 

Scheme 1. Catalytic cycle of the [Ni°L]-catalyzed cyclo-oligomerization of 1,3-butadiene affording Cg-cyclo-oligomer products (according to Wilke et al.) 14...

Scheme 4. Condensed free-energy profile (kcalmol-1) of the complete catalytic cycle of the C8-reaction channel of the nickel-catalyzed cyclo-oligomerization of 1,3-butadiene for catalyst IV with L = P(OPh)3. The favorable [Ni°(p2-tr

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