Synthetic applications of lithium hydroxide

Abstract

(A) Mischne reported a synthesis of [4.4.0] or [5.3.0] bicyclic frameworks achieved via sequential intramolecular Michael-aldol and tandem intramolecular aldol-aldol strategies, starting from acyclic precursors derived from β-ionone. (B) Khim et al. reported that lithium hydroxide induced fragmentation in butenolides and γ-hydroxycyclohexenones. The addition of LiOH (2.0 equiv) to a solution of the carbolactone in THF-H2O (5:1) at room temperature resulted in a mixture of the butenolides and γ-hydroxycyclohexenones in excellent yield. (C) Lemal and co-workers showed that anhydrous lithium hydroxide in benzene transforms tropone into pentafluorotropolone, which functions as a bidentate ligand (72% yield). (D) Yamada et al. reported a lithium hydroxide promoted glucosidation of 1-hydroxyindoles with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide followed by acetylation with Ac2O and pyridine. (E) Tsai et al. showed that lithium base (LiOH) promotes stereoselective Michael addition of thiols to N-methacryloylcamphorsultam and produced the corresponding addition products with a diastereomeric ratio of 66-90%. Hydrolysis of the Michael product with three equivalents of lithium hydroxide in THF-H2O gave the corresponding optically active β-thioester without racemization, and camphorsultam was recovered quantitatively. (F) Lithium hydroxide promotes selective deacylation of diazo-oxazolidones resulting in N-diazoacetyl derivatives. (G) Lattanzi et al. showed a mild and practical procedure of LiOH-promoted HWE olefination, in which aldehydes were reacted with α-cyano phosphonates, yielding α,β-unsaturated nitriles. The reaction conditions are tolerated by functionalized ketones and the exclusive formation of (E)-γ-hydroxy α,β-unsaturated nitriles was observed. (H) Karagiozov and Abbott reported a stereoselective synthesis of α,β-unsaturated esters achieved via HWE reaction of β,β-disubstituted α,β-unsaturated aldehydes. Thus, aldehydes undergo olefination with phosphonate carbanion generated from triethyl phosphonoacetate and lithium hydroxide to give (E)-α,β-unsaturated esters in excellent selectivity. © Georg Thieme Verlag Stuttgart.