International audienceTwo types of indolizidine derivatives can be synthesized from amino-ynones. In the presence of methanesulfonic acid, Meyer-Schuster rearrangement furnished vinylogues of indolizidin-3-ones whereas treatment with zinc chloride gave stable 3-alkynyl-1,5,6,7,8,8a-hexahydroindolizine-zinc complexes that were reduced to 3-alkynylindolizidines

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Amino‐ynones can be seen as precursors of various heterocyclic rings. Although γ‐amino‐ynones have been used to prepare exocyclic vinylogous amides in the presence of Brønsted acids, we describe here the use of zinc chloride as a weak Lewis acid for their conversion into acetylenic cyclic imines. This reaction, which was attempted for a diverse range of γ‐amino‐ynones, proved to be robust and efficient in most cases and was easily extended to δ‐amino‐ynones to yield various acetylenic cyclic imines. Depending on the workup procedure, the latter compounds could be isolated either as free organic compounds or as zinc complexes. The ability of these cyclic imines to form complexes with palladium is also reported.

International audienceWe describe a method that starts from a protected (S)-aspartic acid and employs a gold-catalyzed cyclization to give enantiopure dihydropyridone 2-carboxylates, which are then converted into 6-substituted 4-oxo- and 4-hydroxypipecolic acid derivatives. Thus, the lateral chain carboxylic acid of a commercially available, protected (S)-aspartic acid forms a Weinreb amide, which is then converted into an ynone followed by a gold-catalyzed cyclization to furnish enantiopure enaminones in high yields. The steric hindrance from the protecting group was revealed as an efficient guide for the selectivity of the reduction reactions. Thus, classical methods that use palladium or sodium borohydride afford various enantiopure 6-substituted 4-oxo- and 4-hydroxypipecolic acid derivatives. In these cases, the substituents have an all-cis configuration, whereas a Luche reduction furnishes the 2,4-trans analogues. In the case of the 6-unsubstituted enaminone, the 1,4-addition of a Grignard reagent furnishes the 2,6-trans compound. All 6-substituted 4-hydroxy- and 4-oxopipecolic derivatives were obtained in good yields. The diastereoselectivity for most of the reactions and the ease of separation of the diastereomers, in a few cases, render this method applicable for gram-scale synthesis

A series of quaternary salt derivatives of 2-[(hydroxyimino)methyl]-1-methylimidazole incorporating various side chains bearing ether, silyl, nitrile, ester, halogen, nitro, sulfone, amino, or aminosulfonyl substituents was prepared and evaluated in vivo for the treatment of anticholinesterase intoxication. Test results in the mouse revealed that the type and location of the side-chain substituent both have a significant influence on the toxicity and antidotal effectiveness of the compounds. Some of the more active examples represent the most potent therapeutics to date against intoxication by the powerful cholinesterase inhibitors soman and tabun. Significantly, the antidotal effectiveness of the compounds was not dependent on the inhibiting agent nor was there any correlation between in vivo efficacy and in vitro reactivation of ethyl (4-nitrophenyl)methylphosphonate inhibited human acetylcholinesterase. These observation suggested that the main mode of antidotal protection by the compounds is something other than enzyme reactivation.

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Numerous stable and reactive gold(III) complexes have been described; 1 however, most of them do not present efficient chirality because of their square-planar structure. Recently, the successful introduction of chirality (Fig. 1) has been achieved by two main strategies: the use of chiral BINOL 2 or O,O'-chelated cyclometalated gold(III) complexes 3 (Wong) and the use NHC ligands 4 (Toste). Other complexes, based on bisoxazoline (BOX) and 2-pyridyl-(-) menthol ligands 5 (Fiksdahl) or isothioureas 6 have also been reported. The conception of these chiral gold(III) complexes has allowed catalytic developments. 7

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