Lithio methanes

Various mixed a-halo-lithioalkanes 31 with an additional OR, SR, SOR, SO2R, P(0)(0R)2 substituent in the a-position are available by deprotonation and, in some cases, by halogen-lithium exchange (equation 19). Both methods are also suitable for the generation of halo lithio methanes 32 (equation 20) . ... 

Sequential nucleophilic and electrophilic reactivity of a bromo lithio carbenoid is a feature of the transformation that permits a ring enlargement of cyclic ketones (Scheme 15)367,368 -pijug nucleophilic addition of dibromo lithio methane, which has been generated by deprotonation of dibromomethane, to cyclododecanone 119 leads to the... 

Although the trihalolithiomethanes seem to be predestined to deliver the corresponding dihalocarbenes by spontaneous a-elimination, they have been shown to be stable at temperatures below —100 °C so that they could be characterized by NMR spectroscopy . Furthermore, their nucleophilic reactivity has been demonstrated by the addition to ketones. Herein, the in situ generation of trichloro- and tribromo-lithio-methane 128 and 129 provides a convenient protocol (equation 65) . ... 

However, this process requires a reaction time of 2 days and is inapplicable to unsymmetrical couplings (two different epoxides). As the study described in equation 24 revealed a dramatic solvent effect on similar Brook isomerizations in the adduct of lithio dihalo(triaIkylsilyl)methanes with epoxides (isomerization did not occur following metalation and initial alkylation in THF but proceeded readily upon addition of HMPA), the effect of HMPA for promoting the Brook isomerization was studied once the first alkylation was complete (equation 28) . ... 

Several extensions of these reactions are possible with respect to the electrophilic reagent as well as to the structure of the adduct. Thus functionalized alkyl groups, such as 2-hydroxyethyl and 2-hydroxy-2-phenylethyl, can be introduced into the pyridine ring at the position by treating l-lithio-2-phenyI-l,2-dihydropyridine with ethylene epoxide and styrene epoxide, respectively.144 When polyhalides such as CF3I are used, bis-(substituted-pyridyl)methanes and the dimeric substituted dipyridyls are obtained along with other products.144... 

A number of more readily hydrolysed acetals have been investigated, including lithio bis(methylthio) methanes65 and methoxy phenylthio trialkylsilyl methane (3), which acts as an a-silyl acyl anion equivalent66. This route (Scheme 4) is successful for a wide range of aliphatic electrophiles and is even successful in conjugate addition to enones67. 

Bums and coworkers have discovered a remarkable reaction involving Cp 2U(Me)Cl. Treatment of the latter with l-lithio-l,2-diphenylhydrazine in ether solution generates lithium chloride and methane, and provides the uranium(VI) bis-imido compound Cp 2U(NPh)2, conceivably via a uranium(lV) hydrazido species Cp 2U( ] -PhNNPh)." A plausible reaction sequence is laid out in equations (61) and (62). Cp 2U(NPh)2 was the first uranium(Vl) organometallic complex. In the solid state, Cp 2U(NPli)2 adopts the famihar... 

Methan Lithio- (methoxy-methoxy)-E19d, 912 (SnR3 - Li)... 

Methan Bis-[methylthio]-dimethoxy-phosphoryl-lithio- E19d, 1016... 

Methan Lithio-< 2-[2-(2-methoxy-ethoxy)-ethoxy]-ethyl -methyl-amino)- EI9d, 1045 (SnR3 —> Li)... 

Methan Lithio-phenylthio-trimethyl-silyl- E19d, 954 (SR -> Li)... 

Methan Lithio-diethoxyphosphanyl-(5,5-dimethyl-l,3,2-dioxaphos-phorinan-2-oxid-2-yl)- E19d,... 

---