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[摘要]：Despite steric shielding by the 2,6-di-tert-butylphenyl group ('super-2,6-xylyl' = xyl*), inexpensive sodium phenolate (xyl*-ONa) reacts with dimethyl sulfate to produce only xyl*-OCH3 (94%) with complete suppression of the alternative 4-methylation. Reductive cleavage of xyl*-OCH3 by elemental lithium with the help of an electron carrier generates xyl*-Li, which in turn yields xyl*-CO2H (63%). The corresponding 4-methyl-derivatives of these compounds were obtained analogously. The acid chloride xyl*-COCl (77% yield) acylates HalMgCH(2)R to give only xyl*-COCH3 (86%) or xyl*-COEt (97%). These two ketones react with n-butyllithium (no carbonyl addition) and Cl-PO(OEt)(2) to furnish only the enol phosphates xyl*-C(=CH2)OPO(OEt)(2) (84%) or xyl*-C(=CHCH3)OPO(OEt)(2) (up to 70%), respectively. Only 1,2-elimination occurs when the latter two products are treated with tert-butyllithium, affording xyl*-C CH (68%) or xyl*-C CMe (88%), respectively. |
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