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Regiospecific lithiation

Although 2,5-dibromopyridine may be regiospecifically lithiated at C(5) [149], Pd-catalyzed couplings, including the Sonogashira, Negishi [150], and alkoxycarbonylation reactions [151] all preferentially occur at the C(2) position, as illustrated by the formation of 190. [Pg.221]

Aiylation with a homocuprate. A key step in a synthesis of the cannabis constituent 4 is the reaction of 1 with the homocuprate derived from olivetol dimethyl ether (2) hy regiospecific lithiation followed by reaction with CuBr. The cuprate does not react with 1 in the absence of a Lewis acid, but in the presence of BF, etherate (3.5 equiv.) ( —)-3 is obtained in 78% yield with high regio- and stereospecificity. The dihydrobromide of... [Pg.69]

A careful use of protected primary amino group in regiospecific lithiation reaction has been demonstrated in the following examples... [Pg.138]

Regiospecific lithiation of the methylenedioxy benzylamine indicated followed by quenching with an electrophile (RX) gave a derivative which could be cyclised by acidic treatment to an 8-substituted isoquinoline (ref.102). [Pg.300]

The t-butoxycarbonyl group also favours o-lithiation as in N-(t-butoxy-carbonyl)aniline subsequent reaction with electrophiles provides a route to o-functionalized anilines.Pyridines substituted at the 2- or 3-positions with dialkylcarboxylic acid amides and halogens undergo regiospecific lithiation and then electrophilic attack. In both cases the 2-substituent gives reaction at the 3-position, whereas the 3-substituted pyridine undergoes attack exclusively at the 4-position. The o-lithiated benzamide (15) has been used in the synthesis of polycyclic aromatic hydrocarbons and ellipticine alkaloids by reaction with aromatic aldehydes. ... [Pg.226]

Regiospecific Lithiation Carbonyl Equivalents Alkenyl-lithiums Metal-Lithium Exchange Miscellaneous Reactions... [Pg.396]


See other pages where Regiospecific lithiation is mentioned: [Pg.92]    [Pg.421]    [Pg.216]    [Pg.218]    [Pg.219]    [Pg.4806]    [Pg.94]    [Pg.214]    [Pg.216]    [Pg.390]    [Pg.200]    [Pg.24]    [Pg.49]   
See also in sourсe #XX -- [ Pg.6 , Pg.509 , Pg.510 ]




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Regiospecificity

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