Tetra-t-butylethylene

The McMurry technique of coupling of ketones with titanium(ll) reagents has greatly facilitated attempts to prepare hindered olefins. Although the elusive tetra-t-butylethylene still evades synthesis, more new interesting highly substituted olefins are now available by this technique [e.g. (73)-+(75)]. Other conden-... 

Several research groups are exploring synthetic routes to tetra-t-butylethylene, regarded as the ultimate sterically-hindered olefin, and a number of new tied back relatives have been described. Warner and Jacobson and their co-workers have shown that the gem-dibromocyclopropane (8) undergoes carbene dimerization on treatment with methyl-lithium to give, albeit in low yield, the olefin (9). 

Spectroscopic data indicate that there are no severe non-bonded repulsions in (9), and that the double bond is planar. The groups of Guziec and Krebs have described syntheses of the hindered olefins (10), (11), and (12). Conversion of (10) into tetra-t-butylethylene itself failed when functionalization of the aromatic rings could not be achieved without cleavage of the double bond. ... 

The preparation of strained olefins continues to challenge the synthetic chemist. Although the synthesis of tetra-t-butylethylene remains an elusive goal, the related tetrakis(trimethylsilyl)ethylene has now been prepared and characterized. ... 

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See also in sourсe #XX -- [ ]

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