La reaction de wittig-horner en milieu heterogene VI1. Selectivite de la reaction sur des composes bifonctionnels

Villiéras, J.; Rambaud, M.; Graff, M.

doi:10.1016/s0040-4039(00)98464-8

Cited by 43 publications

(8 citation statements)

References 12 publications

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“…[34][35][36][37][38][39] Further studies have revealed the influence of water and crown ethers on HWE reactions, when using K 2 CO 3 or NaOH as base. [40][41][42] Villieras and colleagues [43][44][45] have used an aq. system of K 2 CO 3 and have found that many HWE reactions of aldehydes and ketones with triethyl phosphonoacetate and with diethyl 2-oxoalkane-phosphonates give the HWE products in good yields at room temperature.…”

Section: Wittig and Horner-wadsworth-emmons-reactions In Biphasic Mediummentioning

confidence: 99%

Wittig- and Horner–Wadsworth–Emmons-Olefination Reactions with Stabilised and Semi-Stabilised Phosphoranes and Phosphonates under Non-Classical Conditions

Jasem

El‐Esawi

Thiemann

2014

Journal of Chemical Research

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Developments in the Wittig and Horner-Wadsworth-Emmons (HWE)-olefination of aldehydes and ketones with stabilised phosphoranes or phosphonates provide opportunities for multicomponent reactions and for reactions with greatly reduced solvent requirements. The in situ preparation of phosphonium salts, phosphoranes or phosphonates and carrying out the reaction and product workup in a biphasic medium can greatly facilitate the reactions. Microwave irradiation and ultrasonication can shorten reaction times considerably. Wittig and HWE reactions have also been carried out in the solid phase, with either polymer-bound reagents or in Wittig reactions with reagents adsorbed on silica or alumina. Good Eand Z-selectivity has been achieved, despite the E/Z-directivity of the carbonyl reagent and of the residue linked to the phosphorane moiety.

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Section: Wittig and Horner-wadsworth-emmons-reactions In Biphasic Mediummentioning

confidence: 99%

Wittig- and Horner–Wadsworth–Emmons-Olefination Reactions with Stabilised and Semi-Stabilised Phosphoranes and Phosphonates under Non-Classical Conditions

Jasem

El‐Esawi

Thiemann

2014

Journal of Chemical Research

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“…Yields are higher at room temperature and when the reaction time increases (Reaction 39). It is also possible to obtain a pheromone secreted by the mandibles glands of the royal bee under PTC conditions in good yield (Reaction 40) [83]. (40) = 81% D.-Q.…”

Section: Ptc Wittig-horner Reactions In Liquid-liquid Systemsmentioning

confidence: 99%

Wittig and Wittig-Horner reactions under phase transfer catalysis conditions

et al. 2003

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Wittig and Wittig-Horner reactions are favorite tools in preparative organic chemistry. These ole nation methods enjoy widespread and recognition because of their simplicity, convenience, and e¯ciency. Phase transfer catalysis (PTC) is a very important method in synthetic organic chemistry having many advantages over conventional, homogenous reaction procedures. In this paper, we attempt to summarize the aspects concerning Wittig and Wittig-Horner reactions that take place under phase transfer catalysis conditions.

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“…64,65,66 Instead of the usual strong and expensive bases, alkali carbonates or hydrogenocarbonates can be used in Wittig-type reactions. 67 For sonochemical applications, no obvious correlation of the reactivity with their lattice energy appears. 68 The reaction applied to the synthesis of cinnamate esters is reasonably rapid even at room temperature, but sonication does not bring about any change in the isomerie ratio.…”

Section: -mentioning

confidence: 99%

Sonochemistry in Biphasic Systems

Loupy

Luche

1998

Synthetic Organic Sonochemistry

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When a choice is possible, reactions in solution are generally preferred to heterogeneous ones, which are considered to create problems with respect, for example, to rates or reproducibility. In many organic reactions, water is an undesirable contaminant. A kind of revolution occurred when Makosza, Starks, and Brändström discovered the principle of phase transfer catalysis (PIC), by which they demonstrated that not only can the presence of water be tolerated but heterogeneity is no longer a drawback. 1 Since these pioneering works, PIe has undoubtedly demonstrated its efficiency and broad applicability.2 Some procedures could be further improved by using solid-supported reagents, sometimes even in the absence of any solvent. 3 Ultrasonic cavitation has particularly important effects on biphasic systems, emulsification of immiscible liquid-liquids, partic1e breakage and dispersion, and surface cleaning in liquid-solid mixtures. These mechanical effects, even if sometimes oversimplified, appear to be understandable and predictable by nonexperts in the field, who exploited them in a variety of heterogeneous reactions. Sonochemistry of biphasic systems then developed rapidly, and synthetic applications were reviewed in recent artic1es. 4 In many cases, the presence of a phase transfer catalyst becomes unnecessary, and sonication can be considered as a "physical substitute to PIe", according to the expression of Ando. 4a Makosza, M. Pure Appl. Chern. 1975, 43, 439-462. 2 For arecent book, see Dehmlow, E.V.; Dehmlow, 5.5. Phase Transfer Catalysis, VCH, Weinheim, 3 rd Ed., 1993.3 For recent reviews, see (a) THE SONOCHEMICAL REACTIVITYFrom the empirical systematization of sonochemistry,9 it is sufficient to remember that, when the possibility exists, radical pathways are privileged at the expense of polar pathways, and sonochemical switching can result in a number of cases.lO In heterogeneous systems, reactions which follow ionic mechanisms are still sensitive to the mechanical effects of sonication. This "false sonochemistry" can, in prindple, also be observed when effident mixing techniques are applied, but the so-called simple mechanical effects are strongly dependent on geometrical factors and prove to be much more complicated than expected.Shocks on solids produce a complex series of events, the final stage of which is heat. Before this frequently useless point is reached, physicochemical transformations occur at the molecular level, especially if mechanical energy is provided faster than heat can be evolved. Vibrational and electronic excitation, bond deformation and breakage, and atom migration are detected by infrared or X-ray spectroscopies. Covalent bonds, for instance in polymers, can be brought to a predissociation state, and their ionization energy is divided by a factor of 2. In a silicon-oxygen-silicon bond system deformed by friction, the reactivity is practi-caUy that of silicon-centered and silyloxy radicals. On surfaces, the energy-rich domains, named "hot spots", are able to initiate chemical reacti...

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La reaction de wittig-horner en milieu heterogene VI1. Selectivite de la reaction sur des composes bifonctionnels

Cited by 43 publications

References 12 publications

Wittig- and Horner–Wadsworth–Emmons-Olefination Reactions with Stabilised and Semi-Stabilised Phosphoranes and Phosphonates under Non-Classical Conditions

Wittig- and Horner–Wadsworth–Emmons-Olefination Reactions with Stabilised and Semi-Stabilised Phosphoranes and Phosphonates under Non-Classical Conditions

Wittig and Wittig-Horner reactions under phase transfer catalysis conditions

Sonochemistry in Biphasic Systems

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