Methanol, photochemical addition

Cyanopyrrole undergoes photochemical rearrangement to 3-cyanopyrrole. If the analogous rearrangement of IV-methyl-2-cyanopyrrole (22) is carried out in methanol, in addition to the 3-cyanopyrrole (24) the bicyclic intermediate (23) is trapped as the methanol adduct (25) (78CC131). 

Octahydro-7-methoxy-l-oxo-lf/-indene-4-carboxylic acids and -4-carboxylates Photochemical Addition of Methanol to Racemic Enones General Procedure24 ... 

The photochemical reactions of the bicyclic compounds (201 a, c) in acetonitrile-methanol solution in the presence of 1,4-dicyanobenzene have been studied. The irradiation of (201a) affords the mixture of trans cis methoxy derivatives (201b) which are also photochemically reactive under the same conditions. The products from (201a) are formed by the photochemical addition of methanol to the furan (202). This furan is formed by production of the radical cation of (201a) followed by deprotonation affording a doubly benzylic radical. The study was extended to the monocyclic system (203) which on electron-transfer-induced irradiation afforded the acetal... 

One of the easiest direct routes to 1-oxygenated menthanes is by direct oxidation of limonene (285). Autoxidation gives a mixture of 1- (540) and 2-hydroperoxides (541), and all of these have now been separated and characterized.Photochemical addition of methanol to give the (3-terpineol... 

The xylene-sensitized photochemical addition of hydroxylic compounds (water or alcohols) to limonene has been described in further detail by Kropp. A 1.2 1 mixture of cis- and tra s-) -terpineol (142a,b R = H) is obtained on irradiation of an aqueous solution containing a trace of xylene, or the corresponding methyl ethers (142a, b R = Me) when methanol is the solvent. A trace of mentha-l(7),8-diene (143) and extensively racemised limonene is also found, supporting the idea that the reaction goes through the symmetrical carbonium ion (141). 3... 

Natsume and Wada " found that photochemical addition of methanol to nico-tinonitrile (426) leads to two dihydropyridines (427 and 428). Both compounds differed in stability only the latter was relatively stable. After 0,N -benzoylation, 429 could be isolated from the mixture as the sole product. Benzamide 429, possessing six carbon atoms in the chain and two differently activated double bonds, appeared to be an interesting substrate for the synthesis of piperidinose-type sugars. 

Two groups have reported on the synthesis of the hydroxymethyl-branched carbocyclic systems 184 (B = Ad, Gua), which can be regarded as ring-enlarged oxetanocin analogues or as carbocyclic analogues of important anti-HIV agents. In one approach, the racemic unit 183 was produced by photochemical addition of methanol to the enone,2i4 whilst other workers reported routes to both 184 and its enantiomer. iS... 

Benefits depend upon location. There is reason to beheve that the ratio of hydrocarbon emissions to NO has an influence on the degree of benefit from methanol substitution in reducing the formation of photochemical smog (69). Additionally, continued testing on methanol vehicles, particularly on vehicles which have accumulated a considerable number of miles, may show that some of the assumptions made in the Carnegie Mellon assessment are not vahd. Air quaUty benefits of methanol also depend on good catalyst performance, especially in controlling formaldehyde, over the entire useful life of the vehicle. 

In addition to these principal commercial uses of molybdenum catalysts, there is great research interest in molybdenum oxides, often supported on siHca, ie, MoO —Si02, as partial oxidation catalysts for such processes as methane-to-methanol or methane-to-formaldehyde (80). Both O2 and N2O have been used as oxidants, and photochemical activation of the MoO catalyst has been reported (81). The research is driven by the increased use of natural gas as a feedstock for Hquid fuels and chemicals (82). Various heteropolymolybdates (83), MoO.-containing ultrastable Y-zeoHtes (84), and certain mixed metal molybdates, eg, MnMoO Ee2(MoO)2, photoactivated CuMoO, and ZnMoO, have also been studied as partial oxidation catalysts for methane conversion to methanol or formaldehyde (80) and for the oxidation of C-4-hydrocarbons to maleic anhydride (85). Heteropolymolybdates have also been shown to effect ethylene (qv) conversion to acetaldehyde (qv) in a possible replacement for the Wacker process. 

There is a scattered body of data in the literature on ordinary photochemical reactions in the pyrimidine and quinazoline series in most cases the mechanisms are unclear. For example, UV irradiation of 4-aminopyrimidine-5-carbonitrile (109 R=H) in methanolic hydrogen chloride gives the 2,6-dimethyl derivative (109 R = Me) in good yield the 5-aminomethyl analogue is made similarly (68T5861). Another random example is the irradiation of 4,6-diphenylpyrimidine 1-oxide in methanol to give 2-methoxy-4,6-diphenyl-pyrimidine, probably by addition of methanol to an intermediate oxaziridine (110) followed by dehydration (76JCS(P1)1202). 

In the case of 1,3-diphenylisoindole (29), Diels-Alder addition with maleic anhydride is readily reversible, and the position of equilibrium is found to be markedly dependent on the solvent. In ether, for example, the expected adduet (117) is formed in 72% yield, whereas in aeetonitrile solution the adduet is almost completely dissociated to its components. Similarly, the addition product (118) of maleic anhydride and l,3-diphenyl-2-methjdi.soindole is found to be completely dissociated on warming in methanol. The Diels-Alder products (119 and 120) formed by the addition of dimethyl acetylene-dicarboxylate and benzyne respectively to 1,3-diphcnylisoindole, show no tendency to revert to starting materials. An attempt to extrude carbethoxynitrene by thermal and photochemical methods from (121), prepared from the adduct (120) by treatment with butyl-lithium followed by ethyl chloroform ate, was unsuccessful. 

Gravel and Leboeuf77 have conducted an extensive photochemical investigation of the thiopyran sulfone (59) and the analogous sulfide. In addition to the isolation of starting material and the product of simple methanol addition (see above), the rearranged sulfone... 

Allyl p-tolyl sulphoxide 535 reacts with sodium methoxide in methanol by initial prototropic isomerization and subsequent addition of methanol to give 536 (equation 333). Protic solvents are photochemically incorporated by the open chain olefinic bond of trans methyl )S-styryl sulphoxide 537 in a Markovnikov regiospecificity (equation 334). Mercaptanes and thiophenols add to vinyl sulphoxides in a similar manner (compare also Reference 604 and Section IV.B.3) to give fi-alkylthio(arylthio)ethyl sulphoxides 538 (equation 335). Addition of deuteriated thio-phenol (PhSD) to optically active p-tolyl vinyl sulphoxide is accompanied by a low asymmetric a-induction not exceeding 10% (equation 336) . Addition of amines to vinyl sulphoxides proceeds in the same way giving )S-aminoethyl sulphoxides in good to quantitative yields depending on the substituents at the vinyl moiety When optically active p-tolyl vinyl sulphoxides are used in this reaction, diastereoisomeric mixtures are always formed and asymmetric induction at the p- and a-carbon atoms is 80 20 (R = H, R = Me) and 1.8 1 (R = Me, R = H), respectively (equation 337) ... 

Additional evidence for a photochemically produced noncarbene precursor to ketene 29 is provided by product analysis. Photolysis of 25 in neat methanol leads to both carbene-derived (i.e., 30 in 75% absolute yield) and ketene-derived adducts (i.e., 31 in 18% absolute yield), but thermolysis of 25 in neat methanol (sealed tube at 170°C) provides only carbene-derived adduct 30 (91% absolute yield) The ratio... 

When similar photolysis of 11 in the presence of MeOD was carried out, again the product whose NMR reveals the resonance due to the Si-H proton was observed. The relative ratio of the Si-H and CH3-0 protons was identical with those of the products obtained in the presence of non-deuterated methanol. The formation of the methoxysilyl group can be understood by the addition of methanol across the silicon-carbon double bonds. H NMR spectra of all photoproducts obtained from the photolyses of 11 in the presence of methanol reveal no resonances attributed to the cyclohexadienyl ring protons. This indicates that the photochemical degradation of the polymer 11 gives no rearranged silene intermediates, but produces... 

Reaction of phthalazinedione 83a with tropone provided adduct 126, which was photochemically transformed into acid 128a in acetonitrile-water solution at room temperature, or to its methyl ester 128b when the reaction was performed in methanol (Scheme 30). Ketene 127 was implicated as the primary intermediate on irradiation and the final products of addition of water and/or methanol 128a and 128b, respectively, were isolated in high yields [72JCS(P1)783]. 

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