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Abstract:The protocol of lithiation by means of lithium and a catalytic (5% molar) amount of DTBB (4,4'-di-tert-butylbiphenyl), applied to ω-chloro ortho ester 6 under Barbier-type conditions gives, after final acid-catalyzed methanolysis, the corresponding functionalized esters 8 or 9 (for chlorotrimethylsilane as electrophile) or, after ortho ester deprotection and acid catalyzed treatment, the δ-lactones 11. The procedure is also practical for bicyclic ortho esters 14: the β-chloro OBO ester derivate generates the γ-lactones 15 and the γ-chloro OBO ester gives corresponding esters 8.

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Imidazole derivatives R 0190Isoprene-Catalyzed Lithiation of Imidazole: Synthesis of 2-(Hydroxyalkyl)-and 2-(Aminoalkyl)imidazoles. -The title reaction is carried out in the presence of a slight excess of Li and catalytic amount of isoprene mostly at room temperature to give the desired products in excellent yields. -(TORREGROSA, R.; PASTOR, I. M.; YUS*, M.; Tetrahedron 61 (2005) 47, 11148-11155; Dep. Quim. Org., Fac. Cienc., Univ. Alicante, E-03080 Alicante, Spain; Eng.) -Y. Steudel 10-136

It is demonstrated that the lithiation of 1‐alkyl imidazoles in the presence of isoprene as a mediator allows the effective preparation of 2‐substituted imidazoles by quenching with carbonyl compounds as electrophiles.

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