Dipyrrolyl alkanes

Unsubstituted pyrrole was reported by Lindsey et al. to react with aldehydes in the same manner as indoles. These reactions were found to be best catalyzed by either lnCl3 or TFA, with the highest conversion and the highest proportion of the meso-substituted dipyrrolyl alkanes from these catalysts. However, a large excess of pyrrole was required, rendering the procedure less practical [131]. Later, the authors made use of alkylthios, easily removed later, to activate the pyrrole and block unwanted substitutions [132]. Most importantly, this new variation had allowed stoichiometric amounts of pyrrole (Figure 8.56). 

An alternative way to form meso-substituted dipyrrolyl alkanes was discovered by Yadav et al, using InBrs (5 mol%) to catalyze the reaction between pyrroles and cyclic enol ethers or enecarbamates [133] (Figure 8.57). InCl3 (10mol%) was also reported to be equally effective. 

Extensive studies on the coordination sphere of the metal using Mo-bisdiphenylamido and dipyrrolyl complexes for olefin metathesis revealed how to improve the activity and selectivity of these catalysts [62-68]. This seminal work led to the synthesis of a new generation of highly active olefin metathesis catalysts [69, 70]. Using a similar strategy, various surface-metal alkylidene and alkylidyne complexes have also been tested in alkane metathesis to determine if they can be employed as catalyst precursors [11, 71]. This section describes the structure-activity relationship of different metal-alkyl complexes with oxide surfaces in alkane metathesis. 

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See also in sourсe #XX -- [ ]

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