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Unsaturated carbonyl derivative synthesis

The Michael addition of nih oalkanes to alkenes substituted with two elecbon-withdrawing groups at the a- and 3-positions provides a new method for the preparation of functionalized alkenes. Although reactions are not new, Ballini and coworkers have used this sbategy in the synthesis of polyfunctionalized unsaturated carbonyl derivatives by Michael addition of nih oalkanes to enediones as shown in Eqs. 7.124-7.126. Success of this type of reaction depends on the base and solvent. They have found that DBU in acetonihile is the method of choice for this puipose. This base-solvent system has been used widely in Michael additions of nitroalkanes to elechon-deficient alkenes (see Section 4.3, which discusses the Michael addition). ... [Pg.220]

R)- and (S)-f-Butyl-5-methylene-l,3-dioxolan-4-one, a Chiral a-Alkoxy Acrylate. It is also possible to introduce an ex-ocyclic double bond onto the dioxolanone ring, as in compounds (9)-(ll), derived from lactic and malic - acids. These a,3-unsaturated carbonyl derivatives are acceptors for radical additions and undergo cycloadditions with dienes and heterodienes. The Diels-Alder adduct (12) of ent-(9) with cyclopentadiene is formed with exo selectivity (96 4) and serves as aprecursor to norbomenone (13). Cycloadduct (14), obtained from methylenedioxolanone (9) and an open-chain triene, is also the result of an exo addition and is used in tetronolide synthesis. ... [Pg.167]

By analogy with cyclopropanes and oxiranes, 2-acylaziridines, aziridine-2-carboxylic esters and amides, are also suitable substrates for one-electron reductive ring cleavage. This is an efficient and highly regioselective method for the synthesis of yS-amino carbonyl compounds. Vinylogous substrates are, furthermore, transformed into <5-amino y8,y-unsaturated carbonyl derivatives azetidines can also be used to achieve y-amino functionalization (Scheme 19) [72]. [Pg.1133]

From a synthetic point of view, the synthesis of a-(perfluoroalkyl)ketones is preferably performed by the reaction of (perfluoroalkyl)phenyliodonium triflates with silyl enol ethers, which affords high yields of the perfluoroalkylated products (104) under mild conditions. The reaction of p,7 unsaturated silyl enol ethers with (perfluoroalkyl)phenyliodonium triflates led to the Y-perfluoroalkyl-a,p-unsaturated carbonyl derivatives (105) in good to high yields.212... [Pg.135]

Chiral auxiliaries having Cj symmetry are very useful in asymmetric synthesis [161] and their role as chiral-protective groups of unsaturated carbonyl derivatives have been examined in an attempt to obtain formal enantioselective cycloadditions, as shown in Scheme 33. [Pg.190]

Snider et al. carried out intensive methodological and synthetic studies in this field. Their synthesis of sesquiter-penoid gymnomitrol by the cyclization of an unsaturated carbonyl derivative 171 with Mn(III) salts to give 172 is depicted in Scheme 25.80. ... [Pg.757]

In the first total synthesis of sequosempervirin A (11), a norlignan isolated from Sequoia sempervirens, the y, 5-unsaturated carbonyl derivative 13 was prepared from 12 by Johnson-Qaisen rearrangement. Further steps led to 14, the precursor of the key RCM reaction catalyzed by (Ru]-I, which established the desired spiro structure of compound 15 (Scheme 1.3). [Pg.2]

Subsequent to Hantzsch s communication for the construction of pyridine derivatives, a number of other groups have reported their efforts towards the synthesis of the pyridine heterocyclic framework. Initially, the protocol was modified by Beyer and later by Knoevenagel to allow preparation of unsymmetrical 1,4-dihydropyridines by condensation of an alkylidene or arylidene P-dicarbonyl compound with a P-amino-a,P-unsaturated carbonyl compound. Following these initial reports, additional modifications were communicated and since these other methods fall under the condensation approach, they will be presented as variations, although each of them has attained the status of named reaction . [Pg.307]

This protocol could be extended to a range of different ,/i-unsaturated carbonyl compounds and either activated or deactivated aryl iodides [22], An application of related Heck chemistry to the synthesis of methylated resveratrol (3,4, 5-trihydroxy-( )-stilbene) is shown in Scheme 6.4 [23]. The phytoalexin resveratrol exhibits a variety of interesting biological and therapeutic properties, among them activity against several human cancer cell lines. Botella and Najera have shown that the trimethyl ether of resveratrol (Scheme 6.4) can be rapidly prepared by microwave-assisted Heck reaction of the appropriate aryl iodide and styrene derivatives, using the same oxime-derived palladacycle as indicated in Scheme 6.3. [Pg.110]

Our own group is also involved in the development of domino multicomponent reactions for the synthesis of heterocycles of both pharmacologic and synthetic interest [156]. In particular, we recently reported a totally regioselective and metal-free Michael addition-initiated three-component substrate directed route to polysubstituted pyridines from 1,3-dicarbonyls. Thus, the direct condensation of 1,3-diketones, (3-ketoesters, or p-ketoamides with a,p-unsaturated aldehydes or ketones with a synthetic equivalent of ammonia, under heterogeneous catalysis by 4 A molecular sieves, provided the desired heterocycles after in situ oxidation (Scheme 56) [157]. A mechanistic study demonstrated that the first step of the sequence was a molecular sieves-promoted Michael addition between the 1,3-dicarbonyl and the cx,p-unsaturated carbonyl compound. The corresponding 1,5-dicarbonyl adduct then reacts with the ammonia source leading to a DHP derivative, which is spontaneously converted to the aromatized product. [Pg.262]

Furan-2-methanols are cleaved to derivatives of levulinic ester by methanolic hydrogen chloride a mechanism involving the carbonium ion (375) has been proposed. Under similar conditions, a,(3- unsaturated carbonyl compounds of type (384) undergo a similar rearrangement, a reaction known as the Marckwald rearrangement, and afford keto esters of type (385), as shown in Scheme 105 in an example drawn from a synthesis of equilenin (70AJC547). [Pg.646]

The two most commonly used types of allyl alcohol linker are 4-hydroxycrotonic acid derivatives (Entry 1, Table 3.7) and (Z)- or ( )-2-butene-l, 4-diol derivatives (Entries 2 and 3, Table 3.7). The former are well suited for solid-phase peptide synthesis using Boc methodology, but give poor results when using the Fmoc technique, probably because of Michael addition of piperidine to the a, 3-unsaturated carbonyl compound [167]. Butene-l,4-diol derivatives, however, are tolerant to acids, bases, and weak nucleophiles, and are therefore suitable linkers for a broad range of solid-phase chemistry. [Pg.55]

According to the classical Hantzsch synthesis of pyridine derivatives, an a,(5-unsaturated carbonyl compound is first formed by Knoevenagel condensation of an aldehyde with a P-dicarbonyl compound. The next step is a Michael reaction with another equivalent of the P-dicarbonyl compound (or its enamine) to form a 1,5-diketone, which finally undergoes a cyclocondensation with ammonia to give a 1,4-dihydropyridine with specific symmetry in its substitution pattern. [Pg.236]

The use of chiral crown ethers as asymmetric phase-transfer catalysts is largely due to the studies of Bako and Toke [6], as discussed below. Interestingly, chiral crown ethers have not been widely used for the synthesis of amino acid derivatives, but have been shown to be effective catalysts for asymmetric Michael additions of nitro-alkane enolates, for Darzens condensations, and for asymmetric epoxidations of a,P-unsaturated carbonyl compounds. [Pg.163]

One of the practically important synthetic pathways to aryl-containing pyrazole derivatives is a reaction of oufi-unsaturatcd ketones with dipolar molecules or 1,2-binucleophiles. There are dozens of stereotypical publications on this topic and in this chapter we will not cite all existing references related to the synthesis and properties of pyrazole derivatives based on unsaturated carbonyl compounds but will cover the most general and some specific examples as well as mechanisms. [Pg.37]


See other pages where Unsaturated carbonyl derivative synthesis is mentioned: [Pg.456]    [Pg.146]    [Pg.889]    [Pg.19]    [Pg.889]    [Pg.2]    [Pg.98]    [Pg.91]    [Pg.196]    [Pg.619]    [Pg.287]    [Pg.411]    [Pg.1119]    [Pg.119]    [Pg.161]    [Pg.317]    [Pg.328]    [Pg.144]    [Pg.498]    [Pg.715]    [Pg.145]    [Pg.145]    [Pg.317]    [Pg.379]    [Pg.290]    [Pg.32]    [Pg.514]    [Pg.545]    [Pg.119]    [Pg.226]   


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Carbonyl derivatives

Carbonylation derivatives

Carbonyls synthesis

Synthesis carbonylation

Synthesis unsaturated

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