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Michael addition Copper catalysed

Copper-catalysed Michael addition followed by an aldol reaction with formaldehyde, gives a 1 1 mixture of diastereoisomers of the aldol 86 that can be eliminated to the enone 83. The resulting efficient photochemical cycloaddition gives ketone 82 with total regioselectivity probably because it is intramolecular. [Pg.135]

Perhaps the major disadvantage of the copper-catalysed Michael reaction is the need to protect functional groups. Michael reactions with heteroatom nucleophiles or functionalised carbon nucleophiles are usually carried out without copper. Many such nucleophiles, particularly enol equivalents, are excellent at Michael reactions, and are often to be preferred for ease of working. Silyl enol ethers, enamines, and stabilised enolates all carry out Michael reactions. In the next chapter we shall look at specific enol equivalents in more detail and note which ones are good at Michael additions. [Pg.136]

A copper catalyst is again used in the Michael addition step. This catalyses Michael rather than direct addition to the ketone and is discussed in the next chapter. Under these conditions the additions is indeed highly stereoselective m favour of the required isomer. Reduction with UAIH4 favoured the axial alcohol as expected. Dioi (25) was used in a synthesis of steroid analogues. [Pg.119]

There are many reports of copper-catalysed conjugate additions (1,4-addi-tions) of organometallic reagents to a,p-unsaturated ketones, which constitute examples of Michael reactions. The model Michael acceptors for cyclic and acyclic substrates are 2-cyclohexen-l-one (37) and zruw -chalcone (38) respectively whereas diethylzinc is the most widely used carbanionic reagent. These model reactions are depicted in Scheme 8.17. [Pg.468]

A copper complex of the NHC ligand (409) has been developed as a catalyst for the Michael addition of pinB-Bpin (pin = pinacol) to a, -unsaturated esters. The adducts were obtained with <89% ee The Rh(III) complex (410) catalysed the same reaction fe with <97% ee ... [Pg.464]

Michael addition of malononitrile and cyanoesters to a, -unsaturated 2-acylimida-zoles, catalysed by a complex of double-stranded DNA and copper(II), has been reported to proceed with <84% eeP ... [Pg.466]

Scheme 7.8 Domino Michael-TEMPO addition reaction catalysed by chiral amine catalysis and copper catalysis. Scheme 7.8 Domino Michael-TEMPO addition reaction catalysed by chiral amine catalysis and copper catalysis.
In 2010, Alexakis and Quintard reported a tandem reaction beginning with a copper-catalysed 1,4-addition of diallqrlzincs to a, 3-unsaturated aldehydes which was followed by an organocatalysed Michael reaction with vinyl sul-fone. ° As shown in Scheme 7.68, this simple procedure, using two chiral entities, such as a chiral copper complex of (I )-BINAP as the first catalyst. [Pg.172]

The annelation of a five-membered to a six-membered-ring, leading to substituted ds-hydrindanes (59), has been accomplished by an intramolecular Michael addition approach, and Marfat and Helquist have described the use of copper-catalysed conjugate addition of the acetal Grignard reagent (60) in... [Pg.237]

Copper The Al-heterocyclic Cu carbene complex (473) has been shown to catalyse the Michael addition of boranes ArCH2CH2BR2, derived fi om styrenes and borabicy-clononane (BBN), to various enones with <91% ee ... [Pg.412]

Nitroalkanes react with Jt-deficient alkenes, for example, p-nitro ketones are produced from a,P-unsaturated ketones [41], whereas allylic nitro compounds have been prepared via the Michael-type addition of nitroalkanes with electron-deficient alkynes (Table 6.19). The reaction in either dimethylsulphoxide [42] or dimethyl-formamide [43] is catalysed by potassium fluoride in the presence of benzyltriethyl-ammonium chloride the reaction with dimethyl acetylenedicarboxylate is only successful in dimethylsulphoxide [42], Primary nitroalkanes produce double Michael adducts [42,44], A-Protected a-aminoacetonitriles react with alkynes under catalysed solidiliquid conditions to produce the Michael adducts [45] which, upon treatment with aqueous copper(Il) sulphate, are converted into a,p-unsaturated ketones. [Pg.281]


See other pages where Michael addition Copper catalysed is mentioned: [Pg.74]    [Pg.83]    [Pg.207]    [Pg.105]    [Pg.224]    [Pg.217]    [Pg.311]    [Pg.313]    [Pg.322]    [Pg.129]    [Pg.36]    [Pg.346]    [Pg.73]    [Pg.119]    [Pg.7]    [Pg.44]    [Pg.340]    [Pg.316]    [Pg.334]    [Pg.412]    [Pg.240]   
See also in sourсe #XX -- [ Pg.562 , Pg.684 ]




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