Amination, of enolsilanes

Enantioselective amination of enolsilanes has also benehted from the use of bis(oxazoline) lignads. " For example, (Z)-l-phenyl-l-(trimethylsilyloxy)-l-pro-pene, 242 was condensed with 243 using copper(ll) triflate-complex bu-box ligand 3 to afford 244 in 95% yield (99% ee) as shown in Figure 9.72. 

Troc = 2,2,2-trichloroethoxycarbonyl Figure 9.72. Enantioselective amination of enolsilanes. 

Enol Amination. The Cu[(S,5)-t-Bu-box] (OTf)2 complex was found to be optimal for promoting the enantioselective conjugated addition of enolsilanes to azodicarboxylate derivatives (eq 13). This methodology provides an enantioselective catalytic route to differentially protected ot-hydrazino carbonyl compounds. Isomerically pure enolsilanes of aryl ketones, acylpyrroles, and thioesters add to the azo-imide in greater than 95% ee. The use of an alcohol additive was critical to achieve catalyst turnover. Amination of cyclic enolsilanes was also possible. For example, the enolsilane of 2-methylindanone provides the adduct containing a tetrasubstituted stereogenic center in 96% ee and high yield. Acyclic (Z)-enolsilanes react in the presence of a protic additive with enantioselection up to 99%. ... 

A catalytic asymmetric amination reaction has been developed using Cu(2+) catalysts (246). The azodicarboxylate derivative 392 reacts with enolsilanes in the presence of catalyst 269c to provide the adducts in high enantioselectivity, Eq. 213. As observed in the Mukaiyama Michael reactions, alcoholic addends proved competent in increasing the rate of this reaction. Indeed, in the presence of tri-fluoroethanol as additive, the reaction time decreases from 24 to 3 h. 

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