Carbonylation tertiary alcohol

The catalysts employed in aldehyde or alcohol synthesis are always based on cobalt while rhodium and nickel are used for the synthesis of acids strong acidic media are employed for tertiary alcohol carbonylation. 

The type of alcohol produced depends on the carbonyl compound Substituents present on the carbonyl group of an aldehyde or ketone stay there—they become sub stituents on the carbon that bears the hydroxyl group m the product Thus as shown m Table 14 3 (following page) formaldehyde reacts with Grignard reagents to yield pri mary alcohols aldehydes yield secondary alcohols and ketones yield tertiary alcohols... 

Tertiary alcohols can be prepared by a variation of the Grignard synthesis that uses esters as the source of the carbonyl group Methyl and ethyl esters are readily available and are the types most often used Two moles of a Grignard reagent are required per mole of ester the first mole reacts with the ester converting it to a ketone... 

Moderate yields of acids and ketones can be obtained by paHadium-cataly2ed carbonylation of boronic acids and by carbonylation cross-coupling reactions (272,320,321). In an alternative procedure for the carbonylation reaction, potassium trialkylborohydride ia the presence of a catalytic amount of the free borane is utilized (322). FiaaHy, various tertiary alcohols including hindered and polycycHc stmctures become readily available by oxidation of the organoborane iatermediate produced after migration of three alkyl groups (312,313,323). 

The behavior of unsaturated azlactones with organometallic reagents has been studied in detail. Arylmagnesium halides and phenyllithium attack 4-arylidene-5-oxazolones at the carbonyl carbon to give ring-opened amido tertiary alcohols (26) and oxazolines (27) (by ring closure), usually as mixtures [Eq. (17)]. The nature of the... 

As examples of their addition to carbonyl compounds, Grignard reagents react with formaldehyde, H2C = 0, to give primary alcohols, with aldehydes to give secondary alcohols, and with ketones to give tertiary alcohols. 

Perhaps the most valuable reaction of alcohols is their oxidation to yield car-bony compounds—the opposite of the reduction of carbonyl compounds to yield alcohols. Primary alcohols yield aldehydes or carboxylic acids, secondary alcohols yield ketones, but tertiary alcohols don t normally react with most oxidizing agents. 

When the carbonyl carbon is substituted with a potential leaving group, the tetrahedral adduct can break down to regenerate a C=0 bond and a second addition step can occur. Esters, for example are usually converted to tertiary alcohols, rather than ketones, in reactions with Grignard reagents. 

As mentioned already, new methylidene-group IV metal complexes have been prepared and were subsequently used in nucleophilic additions to carbonyl electrophiles (Scheme 43).53 In contrast to titanium and zirconium, the reaction of methylidene hafnium dichloride 97 benzophenone stopped at the first stage (i.e., addition). The tertiary alcohol was obtained in 73% yield, while the corresponding alkene was formed only as minor product. 

With ketones, unreactive organozinc species CF3ZnBr and CF3ZnCF3 are mainly formed. In this case, the use of DMF/TMEDA (7 3) as a solvent supresses the formation of the organozinc species and promotes the carbonyl attack, providing tertiary alcohols in moderate yields (Eq. 7) [20]. 

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