Anisolechromium tricarbonyl

Sodium ethoxide in deuterated ethanol was used in a study of the rate of deuteration of anisolechromium tricarbonyl at 100 °C, the first-order coefficient (2.65 x 10 5) being reported as only 3 times greater than that for benzene, cf anisole in the reaction with potassamide in liquid ammonia (Table 177)591a. 

Anisolechromium tricarbonyl, however, is lithiated cleanly ortho to the methoxy gronp, giving products such as 374 Coordination of 375 to Cr(CO)3 changes the regiose-lectivity from the expective cooperatively directed 376 to 377 (Scheme 159). 

Multiple lithiation of anisolechromium tricarbonyl is easy to achieve three equivalents of LUMP give 378 (Scheme 160) 46... 

The enantioselective lithiation of anisolechromium tricarbonyl was used by Schmalz and Schellhaas in a route towards the natural product (+)-ptilocaulin . In situ hthi-ation and silylation of 410 with ent-h M gave ewf-411 in an optimized 91% ee (reaction carried ont at — 100°C over 10 min, see Scheme 169). A second, substrate-directed lithiation with BuLi alone, formation of the copper derivative and a quench with crotyl bromide gave 420. The planar chirality and reactivity of the chromium complex was then exploited in a nucleophilic addition of dithiane, which generated ptilocaulin precnrsor 421 (Scheme 172). The stereochemistry of componnd 421 has also been used to direct dearomatizing additions, yielding other classes of enones. ... 

A similar phenomenon has been observed in the spectra of some diene-iron tricarbonyl compounds (136). The anisolechromium tricarbonyl complex shows loss of 2 H from the [M - 3 CO]+ ion, giving C7H6OCr+, which could have the tropone structure (XIV) while the analogous iso-propoxy complex loses propylene with the probable rearrangement to give... 

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