Michael versatile

The versatility of this reaction is extended to a variety of aldehydes. The bisphenol derived from 2,6-di-/ f2 -butylphenol and furfural, (25) where R = furfuryl (13), is also used as an antioxidant. The utility of the 3,5-di-/ f2 -butyl-4-hydroxyben2yl moiety is evident in stabili2ets of all types (14), and its effectiveness has spurred investigations of derivatives of hindered alkylphenols to achieve better stahi1i2ing quaUties. Another example is the Michael addition of 2,6-di-/ f2 -butyl phenol to methyl acrylate. This reaction is carried out under basic conditions and yields methyl... 

The Michael addition reaction of amines and thiols with bismaleimides or functionalized monomaleimides is a versatile tool ia the synthesis of chain-extended maleimide-terroinated prepolymers. These prepolymers generally are soluble ia organic solvents from which they can be processed to prepreg and molded to high quaUty, void-free laminates. 

The overall process is the addition of a CH-acidic compound to the carbon-carbon double bond of an o ,/3-unsaturated carbonyl compound. The Michael reaction is of particular importance in organic synthesis for the construction of the carbon skeleton. The above CH-acidic compounds usually do not add to ordinary carbon-carbon double bonds. Another and even more versatile method for carbon-carbon bond formation that employs enolates as reactive species is the aldol reaction. 

Seqnendal Michael addidons are versatile methods for the constnicdon of cyclic compounds. Although a variety of these reacdons have been developed, the use of alcohols as nucleophiles for the Michael addidon to nltroalkenes has been little studied. Recently, Dteda and coworkers have reported an elegant synthesis of octahydtobett2o[li furans via the seqnendal Michael addidon of 1-nltro-cyclohexenev/ith methyl4-hydroxy-2-bittynoatein the presence of r-BnOK followed by radical denitradon fEq. 7.74. ... 

Carbonyl condensation reactions are widely used in synthesis. One example of their versatility is the Robinson anuulation reaction, which leads to the formation of an substituted cyclohexenone. Treatment of a /3-diketone or /3-keto ester with an a,/3-unsaturated ketone leads first to a Michael addition, which is followed by intramolecular aldol cyclization. Condensation reactions are also used widely in nature for the biosynthesis of such molecules as fats and steroids. 

In the presence of a catalytic amount of triethylamine, a readily enolizable carbonyl compound like acetylacetone (25) can undergo a Michael-type addition onto the triple bond of 23 with C-C bond formation, and subsequent 1,2-addition of the hydroxy group with elimination of an alcohol (MeOH or EtOH) to eventually yield a pyranylidene complex 28 (mode E) [29]. The most versatile access to / -donor-substituted ethenylcarbene complexes 27 is by Michael-type additions of nucleophiles, including alcohols [30-32], primary... 

Johnson J. S., Evans D. A. Chiral Bis(Oxazoline) Copper(II) Complexes Versatile Catalysts for Enantioselective Cycloaddition, Aldol, Michael, and Carbonyl Ene Reactions Acc. Chem. Res. 2000 33 325-335... 

Nitroolefins are good Michael acceptors and their reactivity toward diethylzinc is different depending on the presence or absence of Lewis acids. Since the nitro group can be further transformed to a variety of useful containing functionalities,76,7641 the asymmetric 1,4-additions of nitroolefins may provide an easily accessible pathway to highly versatile optically active synthons. 

Silylketene acetals and enolsilanes can also undergo conjugate addition to a,/ -unsaturated carbonyl derivatives. This reaction is referred to as the Mukaiyama-Michael addition and can also be used as a mild and versatile method for C-C bond formation. As shown in Scheme 8-34, in the presence of C2-symmetric Cu(II) Lewis acid 94, asymmetric conjugate addition proceeds readily, giving product with high yield and enantioselectivity.75... 

Donor- and acceptor-substituted allenes with general structures 1 or 2 (Scheme 8.1) have the most obvious synthetic potential among functionalized allene derivatives and therefore they serve as versatile building blocks in many synthetic endeavors [1], As expected, the reactivity of the double bonds of 1 or 2, which are directly connected to the activating substituents, are strongly influenced by these groups. Hence there is enol ether or enamine reactivity of 1 and Michael acceptor type chemistry of 2. In addition, the terminal double bonds are also influenced by these functional groups. 

Nitroalkenes are excellent Michael acceptors, and asymmetric 1,4-additions to nitroalkenes (Scheme 7.22) provide access to highly versatile synthons, since the nitro group is readily reduced to the corresponding amine [74]. Seebach, employing a... 

The wide range of Michael donors and acceptors in 1,4-additions are of great utility. Consequently, fnrther exploration on the addition of a-snbstituted P-ketoester addition to a,p-nnsatnrated ketones have captured the attention of many chemists. The transformation is a versatile methodology to access all-carbon qnatemary stereocenters. 

The conjugate addition of nitro olefins under chiral Cmc/mna-thiourea catalysis has shown promising results with a variety of Michael donors. Dixon conducted a screen of various chiral thioureas and identified catalyst 117 as a versatile catalyst that works well with p-substituted nitro-olefms (78) [74]. Aromatic, heteroaromatic... 

The Michael additions to 1 - 3 of a large variety of carbon, nitrogen, oxygen, sulfur and selenium nucleophiles, as well as hydride, followed by inter- or intramolecular transformations of the chlorine substituent or/and the methoxy-carbonyl fragment, offer versatile synthetic approaches to a large variety of synthetically useful and important organic molecules. 

Phenylsulfonyl-1,3-dienes are versatile synthetic intermediates. They can participate in cycloaddition reactions and Michael-type additions leading to adducts which can be further functionalized. In the latter case the resulting allylic sulfone can be functionalized by electrophiles, nucleophiles, or both (Figure 1). 

The developmenf of self-curing resins, i.e., systems curing without photoinitiators or, in some cases, with just small amounts of photoinitiators, has been reported recently. Such resins are synthesized by Michael reaction of acrylic functional materials with Michael donor compounds such as acetoacetates. The resulting product has an increased molecular weight compared to the parent acrylate(s). This provides resins with reduced volatility and propensity for skin absorpfion. This new technology is versatile and flexible and opens a possibility of synfhesis of a large number of different acrylate resins. The novel resins reportedly exhibit unique depth of cure capability. In the absence of a photoinitiator (PI), film of approximately 10 mils (0.25 mm) thick can be cured at a line speed of 100 fpm (30.5 m/min). When only 1% of PI is added, the thickness of film that can be cured increases to over 100 mils (2.5 mm). 

Aliphatic nitro compounds are versatile building blocks and intermediates in organic synthesis,14 15 cf. the overview given in the Organic Syntheses preparation of nitroacetaldehyde diethyl acetal.16 For example, Henry and Michael additions, respectively, lead to 1,2- and 1,4-difunctionalized derivatives.14 18 1,3-Difunctional compounds, such as amino alcohols or aldols are accessible from primary nitroalkanes by dehydration/1,3-dipolar nitrile oxide cycloaddition with olefins (Mukaiyama reaction),19 followed by ring cleavage of intermediate isoxazolines by reduction or reduction/hydrolysis.20 21... 

Nitroketones are reduced to pyrroles by diphenyl disulfide and triphenylphosphine (86JCS(Pl)2243). Since 7-nitroketones are accessible by Michael additions of nitroalkanes to enones, this is a potentially versatile method (Scheme 40). 

Michael addition of amines to bis(acrylamides) has provided a versatile method for the preparation of poly(amidoamines) (70MH1102). A wide variety of piperazine-containing polyamides may be prepared by this route when a piperazine, 1,4-diacryloylpiperazine... 

Much milder conditions are used in the double Michael addition approach, in which a divinyl ketone is condensed with hydrogen sulfide in mildly basic medium (equation 77) (77JOC2777). Enol acetates (R1 = MeCC>2) may be used, and the product obtained then contains a 2-mercapto function (R1 = SH see also equation 82) (59% yield). Although this is a very versatile synthesis, its biggest drawback is the lability of simple divinyl ketones, and phenyl substitution at position 2 is frequently used to overcome this. 

Chlorocyclopropylidenacetates are versatile starting materials in the synthesis of cyclic terpenoid systems255. In the methyl ester (154), the two independent molecules lie in mirror planes in the orthorhombic Pnma crystal, thus the heavy-atom skeletons are completely planar255. The distal bond, 1.548 (8) A, and the vicinal bonds, 1.453 (7), 1.457 (7) A, have the same lengths as in 142 the C=C bond is shortened to 1.311 (7) A. Reactivity in Diels-Alder and Michael additions cannot be directly deduced from the geometrical features. 

---