Condensation in recyclable water between aldehydes or ketones and amines occurs smoothly within the hydrophobic cores of nanomicelles, resulting in imine formation that is subject to subsequent reduction leading, overall, to reductive amination. This micellar technology enables the synthesis of several types of pharmaceuticals, a new procedure that relies on only 2000 ppm (0.20 mol %) palladium from commercially available Pd/C. A broad range of substrates can be used under mild conditions, leading to high chemical yields of the desired secondary and tertiary amines.
1,2,4,5-Tetrasubstituted-1H-imidazoles are a large family of heteroarene derivatives that are known to include natural products isolated from marine sponges and synthetic compounds possessing a broad range of biological and pharmacological properties. Consequently, a great deal of attention has been given to the synthesis of these heteroarenes and reviews covering some synthetic aspects of this topic have been published in recent years. However, none of these reviews provides a comprehensive overview of the several catalytic methods developed in the literature for the preparation of this important class of heteroarenes. This article review with 469 references, 63% of them being related to the period 2010-2017, aims to provide an updated critical picture of the catalytic processes reported in the literature up to the end of 2017 for the synthesis of 1,2,4,5-tetrasubstituted-1H-imidazoles illustrating these protocols and their characteristic features such as scope, efficiency, versatility, and limitations. The review also summarizes the mechanisms of the catalytic processes proposed for many of the reported processes.
An inexpensive and new triphenylphosphine‐based palladacycle has been developed as a pre‐catalyst, leading to highly effective Stille cross‐coupling reactions in water under mild reaction conditions. Only 500–1000 ppm of Pd suffices for couplings involving a variety of aryl/heteroaryl halides with aryl/hetaryl stannanes. Several drug intermediates can be prepared using this catalyst in aqueous nanoreactors formed by 2 wt % Brij‐30 in water.
A catalytic amount of silver acetate efficiently promotes direct insertion of zinc metal into aryl iodides, having different structure, in ethereal solvent. Electron‐rich substrates also rapidly undergo oxidative metalation. The arylzinc iodides formed give Negishi coupling products under mild reaction conditions to obtain biaryls in high yields. Sensitive functional groups like aldehydes and primary amides are well‐tolerated.
The reaction mechanism of a new conjugate addition reaction of organozinc halides to enones is disclosed by a combined experimental/computational study.
Graphical AbstractIdentification and synthesis of new sex specific components of olive fruit fly (Bactrocera oleae) female rectal gland, through original Negishi reactions on supported catalysts Identification and synthesis of new sex-specific components of olive fruit fly (Bactrocera oleae) female rectal gland, through original Negishi reactions on supported catalystsIn the present study, eleven new sex-specific components extracted from female rectal gland of olive fruit flies were synthesized and identified. The quantitative determination of those components by GC and GC/EI-MS, at different moments of the insect life span, highlighted the growing trend of their secretion. While for the synthesis of saturated esters, conventional transesterification methods could be adopted, for the synthesis of unsaturated components, a Negishi cross-coupling between organozinc halides and (Z)-1-bromo-alkenes was developed. To the extent of our knowledge, this reaction represents the first example of catalyst-supported Negishi coupling, between an alkyl electron donor and an alkenyl electron acceptor..
Pterostilbene, an important polyphenolic compound with interesting biological activities, has been efficiently synthesized through a Mizoroki-Heck reaction catalyzed by supported Palladium catalyst. The synthesis has been transposed in a continuous flow reactor, following two different retrosynthetic approaches.
An inexpensive and new triphenylphosphine‐based palladacycle has been developed as a pre‐catalyst, leading to highly effective Stille cross‐coupling reactions in water under mild reaction conditions. Only 500–1000 ppm of Pd suffices for couplings involving a variety of aryl/heteroaryl halides with aryl/hetaryl stannanes. Several drug intermediates can be prepared using this catalyst in aqueous nanoreactors formed by 2 wt % Brij‐30 in water.
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