Nucleophilic addition reactions tertiary alcohol formed from

This reaction has been modified by treatment of em-trichloromethyl-substituted tertiary alcohols (generated from the nucleophilic addition of trichloromethide), e.g., CHCI3 + LHMDS) by sodium azide and an organic base (e.g., DBU) in alcohol to form a-azido ester in a one-pot manner. The resulting a-azido ester can then be selectively converted into a-azido alcohol with cold NaBH4. ... 

The stereochemical outcome of the addition of carbanions to ketones yielding tertiary alcohols (or secondary alcohols in the case of aldehydes) is variable and depends on the substrate, the counterion and the solvent. Numerous applications of this strategy to natural product synthesis from carbohydrates can be found in the literature and this approach was fruitful in pioneering syntheses of polyketide-type products. Here again, the template effect of the sugar plays a tremendous role in the stereochemical outcome of the reaction. Chelation controlled nucleophilic addition can also be used to form chiral centers in a highly predictable way. 

Rapopoit found that 5-(2-pyridyl) thioates such as (28) did not function as selective acylating agents, and substantial amounts of tertiary alcohol were formed through overaddition (equation 16). Presumably, the tetrahedral intermediate, derived from nucleophilic addition to the S-(2-pyridyl) thioate, was not a stable entity in the reaction mixture. As will be discussed shortly, the lability of these intermediates had been recognized previously. The novel dimethylpyrazolide moiety of substrate (29) also did not confer any additional stability to the tetrahedral intermediate and tertiary alcohol was the major product (equation 16). Tertiary amides, such as those derived from pyrrolidine or dimethylamine, were reactive towards lithium adkynides in the presence of BF3, but analysis of the product indicated that it had undergone substantial racemization. ... 

The acyliion(O) complex (102) has been isolated and subjected to the same nucleophilic displacement (or equivalently oxidative addition) with excellent correlation (Scheme 39). The same species is also readily available from acid chlorides (i.e. formation of 103), but the overall process has not been widely used in the synthesis of ketones (Scheme 40).The final step of the process, a reductive elimination of acyliron(II) complex (104) or (105), is quite rapid and it has not been possible to isolate and identify the presumed intermediates in this case (Scheme 41). Since the oxidative addition of the acyliron complex with the alkyl halide is extremely mild, the corresponding ketone formed in the reaction is not subject to attack by organometallic reagents and no tertiary alcohol is formed. 

All the C-F bonds of primary, secondary, and tertiary a-fluorohydrazones, a,a-difluoro-, and a,a.a-trifluorohydrazones react with a wide variety of nucleophiles including alcohols, alkoxide ions, amines, mercaptans, and carbon nucleophiles in the presence of K2CO3 in yields ranging from 32 to 97%. The 5N2-type product formed by reaction of the C-F bond is actually formed by an elimination-addition mechanism. 

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