Metal-template synthesis

Blanco, M.-J., Transition-Metal-Templated Synthesis of Rotaxanes, 23, 125. 

Aucagne V, Bema J, Crowley JD, Goldup SM, Hanni KD, Leigh DA, Lusby PJ, Ronaldson VE, Slawin AMZ, Viterisi A, Walker DB (2007) Catalytic active-metal template synthesis of [2]rotaxanes, [3]rotaxanes, and molecular shuttles, and some observations on the mechanism of the Cu(I)-catalyzed azide-alkyne 1, 3-cycloaddition. J Am Chem Soc 129 11950-11963... 

A Novel Metal-Template Synthesis of Triphosphine Macrocycles... 

Scheme 40. Metal-templated synthesis of an acetone-aldolate ligand...

Fallis and Heuft have used a metal-templated synthesis to form the helical 1,10-phenanthroline-capped metal-complexed SPMs 87 and 88 (Scheme 6.20) and their demetalated analogs (not shown). The addition of [Cu(OAc)2] (0.5 equiv) to a solution of 89 in pyridine and diethyl ether templated the formation of intermediate 90. Following the addition of excess [Cu(OAc)2] (5.5 equiv), the Cu(I)-complexed SPM 87 was isolated in an excellent yield of 84%. Treatment of 87 with aqueous KCN then provided the Cu-free SPM in 70% yield (not shown). The N,N-dibutylamine substituted analog 88 was formed in an analogous manner and taken on directly to the Cu-free SPM (39%) in a one-pot procedure. It was shown by variable temperature 13C NMR spectroscopy that the helical Cu(I) complex 88 had a barrier to racemiza-tion of 4 kcal mol 1 higher than that of the Cu-free analog [83]. 

This chapter will be concerned mainly with the transition-metal-templated synthesis of rotaxanes. General features of these compounds, including stereochemical issues, will be addressed at first. The intent, however, is not to... 

III. TRANSITION-METAL-TEMPLATED SYNTHESIS A. Principle and Examples... 

Figure 2.22. Strategies for the transition metal-templated synthesis of catenanes. The metal (in) predisposes two fragments as open chelates (A) (strategy I) or as a macrocyclic chelate (E) and an open chelate (strategy II) in intermediates (B) and (F), respectively. Cyclization of these intermediate complexes with the chain fragments (C) provides the [2]-catenate complex (D).

Figure 2.24. Schematic representation of the principle of transition-metal-templated synthesis of [2]-rotaxanes from macrocyclic chelate (A), metal cation (black disk) and open chelate (B). The latter bears functions X at its extremities, which will be used for anchoring or constructing the stoppers (represented as diamonds). (/) Threading step (//) stoppering step (in) removal of the metal template.

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