Lithium compounds Alcohol

Most commercial liquid ammonia contains up to several ppm of colloidal iron compounds, possibly the iron oxide catalyst commonly used in manufacturing ammonia. Reduction converts these compounds to colloidal iron which strongly catalyzes the reaction between alcohols and sodium and potassium. The reaction of lithium with alcohols is also catalyzed by iron but to a markedly lesser degree. The data in Table 1-4 illustrate the magnitude of these catalytic effects. The data of Table 1-5 emphasize how less than 1 ppm... 

Among other fluoroaromatic lithium compounds, 2,2 -dilithioperfluoro-biphenyl was investigated No secondary alcohols as mentioned previously m similar reactions are noted in any examples [55]... 

The same alcohols can be produced using the lotzich method by boiling the lotzich complex (ethynyl magnesium or lithium compound in ether) with a small excess of carbonyl compound. However, the yields of the alcohols obtained by this method are somewhat lower (47-53%) (68KGS695) (Scheme 60). 

The rearrangement of an ether 1 when treated with a strong base, e.g. an organo-lithium compound RLi, to give an alcohol 3 via the intermediate a-metallated ether 2, is called the Wittig rearrangement. The product obtained is a secondary or tertiary alcohol. R R can be alkyl, aryl and vinyl. Especially suitable substrates are ethers where the intermediate carbanion can be stabilized by one of the substituents R R e.g. benzyl or allyl ethers. 

The breakthrough was achieved by D. A. Evans and coworkers " , who demonstrated that aryldimethylphosphine-borane complexes 195 are easily deprotonated by i-BuLi/(—)-sparteine (11), furnishing efficient enantiotopic selection between the methyl groups (equation 45). The intermediate lithium compound 196 was added to benzophenone (to give alcohols 197) or oxidatively coupled to furnish bisphosphines 198 with high ee. The major amount of the minor diastereomer epi-196 is removed as separable meso- 9. ... 

The preparation of a primary alcohol from an organo-lithium compound and formaldehyde. 

Also other reaction types have been dealt with in CHEC(1984) and CHEC-II(19%) like reduction to alcohols (e.g., sodium borohydride), Wolff Kishner reduction, nucleophilic addition via reaction with Grignard reagents or organo-lithium compounds, and formation of imine type functional groups (e.g., hydrazones). New examples are the reaction of... 

Mansson 319) has also investigated the products of the reaction of poly(styryl)-lithium with oxygen. Although products with carbonyl and alcohol functionality were detected, they may have resulted from the column and thin layer chromatographic work-up procedures employed. In conclusion, the oxidation of polymeric organo-lithium compounds is complex, but the possibility of manipulating the reaction conditions to form useful macroperoxides and hydroperoxides is real, as evidenced by the work of Brossas and coworkers 350). 

Acyl anions (RC(=0)M) are unstable, and quickly dimerize at temperatures >-100 °C (Section 5.4.7). These intermediates are best generated by reaction of organolithium compounds or cuprates with carbon monoxide at -110 °C and should be trapped immediately by an electrophile [344—347]. Metalated formic acid esters (R0C(=0)M) have been generated as intermediates by treatment of alcoholates with carbon monoxide, and can either be protonated to yield formic acid esters, or left to rearrange to carboxylates (R0C(=0)M —> RC02M) (Scheme 5.38) [348]. Related intermediates are presumably also formed by treatment of alcohols with formamide acetals (Scheme 5.38) [349]. More stable than acyl lithium compounds are acyl silanes or transition metal acyl complexes, which can also be used to perform nucleophilic acylations [350],... 

Fig. 17.47. Reductive lithiation of a carbamoyl chloride to the (dialkylamino)carbonyl lithium compound A and its immediately following reaction with a carbonyl compound (Barbier reaction) leading to alcohol B.

The reactions of arylmagnesium and aryllithium compounds are similar and are analogous to the reactions of the corresponding alkyl species. These reagents are strong bases, particularly the lithium compounds, and react rapidly with weak acids such as water and alcohols to form the arene. It is therefore important when using these reagents that reactants, solvents and apparatus are dry and free of acid. 

This disconnection represents the retro-Grignard reaction. It leads almost automatically to organomagnesium or lithium compounds as equivalents of carbanions and aldehydes or ketones as equivalents to the carbocation in the synthesis of alcohols (Scheme 2.35), or carbon dioxide in the synthesis of carboxylic acids. 

The reaction with oxirane, affording 0-F—C6H4—CH2CH2OH, can be carried out in a similar way and gives the alcohol in a reasonable (about 70%) yield. Oxirane is added in an excess of 30 %. In the absence of HMPT the reaction is very slow. Couplings with aldehydes and ketones or thiolation with elemental sulfur have to be carried out with the lithium compound, which can be prepared as indicated, or by addition of a solution of anhydrous LiBr in THF to the solution of the potassium compound. f-BuOLi present in the solution may give rise to aldol condensation of enolizable aldehydes and ketones, particularly at temperatures in the region of 0 °C. Therefore, the use of an excess of the aldehyde or ketone should be avoided. 

In the subsequent 12 steps (Scheme 4) the two primary alcohol functions in 24 are oxidized to carboxyl functions and protected as benzyl esters. After trimethylsilyl(TMS)-pro-tection of the OH group at C4 Nicolaou then obtains the aldehyde 30. Addition of the lithium compound prepared from the dithiane 31 to the Cl side chain (Scheme 5) of 30 deli-... 

Alkylbenzothiazoles, like 2-alkylthiazoles, are CH-acidic. They are deprotonated by -butyl-lithium in THF at -78°C. The lithium compounds react with aldehydes or ketones giving alcohols [102], e.g. ... 

The addition of lithiimi 1-oxyalkanides 26a to the carbonyl group of aldehydes and ketones usually takes place with very low enantiofacial differentiation, giving rise to mixtures of (half-protected) syn- and awfi-diols 27 [Eq. (lOa)j [16,17]. A slight improvement is achieved in the presence of magnesium bromide [17]. Even the strained lithium compound 29, bearing a lactone moiety, could be prepared via lithiodestannylation of 28 and was added onto the enal 30 to give the allylic alcohol 31 during the synthesis of the taxol ABC system [Eq. (lOb)] [18]. 

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