Oxidation-Diels-Alder reaction

Table 4.19 Multiple hydroxylation-oxidation Diels-Alder reactions initiated by tyrosinase...

Oxidative-pericydic processes, and in particular the oxidative/Diels-Alder reaction, are quite common in nature. The so-called Diels-Alderase is usually an oxidizing enzyme, which induces, for example, the formation of a suitable dienophile such as an enone from an allylic alcohol [49]. 

If the oxidation is performed in the presence of an external dienophile, the respective products of [4+2] cycloaddition are formed [351-356]. Typical examples are illustrated by a one-pot synthesis of several silyl bicyclic alkenes 283 by intermolecular Diels-Alder reactions of 4-trimethylsilyl substituted masked o-benzoquinones 282 generated by oxidation of the corresponding 2-methoxyphenols 281 [351] and by the hypervalent iodine-mediated oxidative dearomatization/Diels-Alder cascade reaction of phenols 284 with allyl alcohol affording polycyclic acetals 285 (Scheme 3.118) [352]. This hypervalent iodine-promoted tandem phenolic oxidation/Diels-Alder reaction has been utilized in the stereoselective synthesis of the bacchopetiolone carbocyclic core [353]. 

In 2006, Wood described a tandem aromatic oxidation/Diels-Alder reaction for the synthesis of the earboeyclic core of bacchopetiolone. Oxidation of substituted phenol 102 with bis(trifluoroacetoxy)-iodobenzene (BTIB) provides bicycle 103 that dimerizes via a Diels-Alder reaction to yield polycyclic 104, which is two decarbonylations away from the target natural product. ... 

In 2012, Christmann et al. developed an enantioselective tandem oxidation-Diels-Alder reaction of a trienol which constituted the key step in the synthesis of the key decalin subunit of UCS1025A. The first step of this one-pot process was a copper-catalysed oxidation of this trienol into... 

Scheme 7.69 Tandem oxidation-Diels-Alder reaction catalysed by copper catalysis...

Scheme 21 Preparation of 7-thiabicyclo[2.2. l]hept-2-en-7-oxides through oxidative Diels-Alder reaction from 3,4-diaryllthiophenes and representative compounds for selective activity to ERo [3]...

A comparison of the wt-CPBA oxidized Diels-Alder reaction of thiophene derivatives with A -phenylmaleimide, with or without Lewis acid, showed that the overall yields of Diels-Alder products in the presence of /n-CPB A are much lower than those using /M-CPBA/BF3 Et20 complex, suggesting that the Lewis acid catalyst enhances the yield of the oxidative cycloaddition of thiophenes considerably [13],... 

Scheme 42 Oxidative Diels-Alder reaction of 3-bromo-5-methyl[8](2,4)metathiophenophane with dimethyl acetylenedicarboxylate [16]...

W C, A Tempcz)rrk, R C Hawley and T Hendrickson 1990. Semianalytical Treatment of Solvation for Molecular Mechanics and Dynamics. Journal of the American Chemical Society 112 6127-6129. ensson M, S Humbel, R D J Froese, T Matsubara, S Sieber and K Morokuma 1996. ONIOM A Multilayered Integrated MO + MM Method for Geometry Optimisations and Single Point Energy Predictions. A Test for Diels-Alder Reactions and Pt(P(t-Bu)3)2 + H2 Oxidative Addition. Journal of Physical Chemistry 100 19357-19363. 

Cyclohexene derivatives can be oxidatively cleaved under mild conditions to give 1,6-dicarbonyl compounds. The synthetic importance of the Diels-Alder reaction described above originates to some extent from this fact, and therefore this oxidation reaction is discussed in this part of the book. 

Diels-Alder Reaction. In 1928, Diels and Alder discovered that 1,3-unsaturated organic compounds reacted with quinoid systems to give partially hydrogenated, cycHc compounds. In the course of their work, they found that 1 mol of 1,4-naphthoquinone [130-15-4] reacted readily with 1 mol of 1,3-butadiene [106-99-0] to give a partially hydrogenated anthraquinone (11) l,4,4a,9a-tetrahydro-9,10-anthracenedione [56136-14-2] which, on oxidation with chromic oxide, produced anthraquinone (43) ... 

Sorbic acid is oxidized rapidly in the presence of molecular oxygen or peroxide compounds. The decomposition products indicate that the double bond farthest from the carboxyl group is oxidized (11). More complete oxidation leads to acetaldehyde, acetic acid, fumaraldehyde, fumaric acid, and polymeric products. Sorbic acid undergoes Diels-Alder reactions with many dienophiles and undergoes self-dimerization, which leads to eight possible isomeric Diels-Alder stmctures (12). 

When the Diels-Alder reaction between butadiene and itself is carried out in the presence of alkah metal hydroxide or carbonate (such as KOH, Na2C02, and K CO on alumina or magnesia supports) dehydrogenation of the product, vinylcyclohexene, to ethylben2ene can occur at the same time (134). The same reaction can take place on simple metal oxides like Zr02, MgO, CaO, SrO, and BaO (135). 

The dimer acids [61788-89-4] 9- and 10-carboxystearic acids, and C-21 dicarboxylic acids are products resulting from three different reactions of C-18 unsaturated fatty acids. These reactions are, respectively, self-condensation, reaction with carbon monoxide followed by oxidation of the resulting 9- or 10-formylstearic acid (or, alternatively, by hydrocarboxylation of the unsaturated fatty acid), and Diels-Alder reaction with acryUc acid. The starting materials for these reactions have been almost exclusively tall oil fatty acids or, to a lesser degree, oleic acid, although other unsaturated fatty acid feedstocks can be used (see Carboxylic acids. Fatty acids from tall oil Tall oil). 

Oxidation of thiophene with peracid under carefully controlled conditions gives a mixture of thiophene sulfoxide and 2-hydroxythiophene sulfoxide. These compounds are trapped by addition to benzoquinone to give ultimately naphthoquinone (225) and its 5-hydroxy derivative (226) (76ACS(B)353). The further oxidation of the sulfoxide yields the sulfone, which may function as a diene or dienophile in the Diels-Alder reaction (Scheme 88). An azulene synthesis involves the addition of 6-(A,A-dimethylamino)fulvene (227) to a thiophene sulfone (77TL639, 77JA4199). 

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

Other methods for the preparation of cyclohexanecarboxaldehyde include the catalytic hydrogenation of 3-cyclohexene-1-carboxaldehyde, available from the Diels-Alder reaction of butadiene and acrolein, the reduction of cyclohexanecarbonyl chloride by lithium tri-tcrt-butoxy-aluminum hydride,the reduction of iV,A -dimethylcyclohexane-carboxamide with lithium diethoxyaluminum hydride, and the oxidation of the methane-sulfonate of cyclohexylmethanol with dimethyl sulfoxide. The hydrolysis, with simultaneous decarboxylation and rearrangement, of glycidic esters derived from cyclohexanone gives cyclohexanecarboxaldehyde. 

Literature articles, which report the formation and evaluation of difunctional cyanoacrylate monomers, have been published. The preparation of the difunctional monomers required an alternative synthetic method than the standard Knoevenagel reaction for the monofunctional monomers, because the crosslinked polymer thermally decomposes before it can revert back to the free monomer. The earliest report for the preparation of a difunctional cyanoacrylate monomer involved a reverse Diels-Alder reaction of a dicyanoacrylate precursor [16,17]. Later reports described a transesterification with a dicyanoacrylic acid [18] or their formation from the oxidation of a diphenylselenide precursor, seen in Eq. 3 for the dicyanoacrylate ester of butanediol, 7 [6]. 

Alkynes substituted with one or two trifluoromethyl groups are also highly reactive dienophiles [9] Indeed, hexafluoro-2-butyne is used increasingly as a definitive acetylenic dienophile in "difficult Diels-Alder reactions. It was used, for example, to prepare novel inside-outside bicycloalkanes via its reaction with cir,trnns -l,3-undecadiene [74] (equation 67) and to do a tandem Diels-Alder reaction with a l,l-bis(pyrrole)methane [75] (equation 68) Indeed, its reactions with pyrrole derivatives and furan have been used in the syntheses of 3,4-bis(tri-fluoromethyl)pyrrole [76, 77] (equation 69) and ],4-bis(trifluoromethyl)benzene-2,3-oxide [78] (equation 70), respectively. 

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