Oxime acrylates

Another important consideration was the fact that the absorption maxima of oxime acrylate monomers could be tuned to the desired wavelength by the selection of desired ketone or aldehyde chromophore from whence the oxime was originally synthesized. In our design, UV photocrosslinking followed dye-sensitized visible polymerization which formed a soft gel. It is very important to be able to choose the absorption window for the crosslinking reaction to prevent interfering absorption, if any, from the residual dye initiator. Acyl oximes as part of the backbone of a photodegrading polymer chain have been studied by Smets [217],... 

Table 6 lists the absorption characteristics of the series of UV-sensitive monomers investigated [218]. Aliphatic oxime acrylates show absorption maxima below 230 nm, while benzophenone oxime acrylate shows an absorption maximum at 252 nm. It is important to note that while benzophenone has absorption at 360 nm owing to the n-n transition, the corresponding oxime has no strong absorption above 300 nm. Pyrene-1-carboxaldehyde oxime acrylate (POA) and 9-phenanthrenecarboxaldehyde... 

To demonstrate the UV crosslinkability of the polymers formed having pendant acyloxyimino groups, copolymers of bisphenol diacrylate and 1,6 hexanediol diacrylate were prepared by thermal methods with 5% (by weight) of pyrene oxime acrylate and phenanthrene oxime acrylate, both of which have considerable absorption in the region of 320-360 nm. The polymerization was stopped before the gel point and the prepolymer solutions were then irradiated with light from a monochromator at the maximum of... 

Copolymers of styrene with acetophenone oxime acrylate were produced using benzophenone as a sensitiser . The total number of amino groups was found to be unaffected by the nature of the atmosphere. Organic dyes have been found to sensitise the photopolymerisation of a polyimide using the tetra-t-butylperester... 

Another [3+2]-cycloaddition process that has proven value in the construction of macrocyclic natural products, but has been underexplored to date for medicinal chemistry purposes, is the intramolecular addition of nitrile oxides (typically generated in situ from the corresponding oxime) with alkenes (Scheme 11.23). For example, this reaction has been employed for the conversion of oxime-acrylate 172 into 173, an intermediate for the synthesis of the macrosphelide skeleton, and for the construction of macrocycles useful in studies directed towards an asymmetric synthesis of brefeldin... 

Ammonia also reacts with the acrolein intermediate, via the formation of an imine or possibly oxime intermediate which transforms faster to the acrylonitrile than to the acrylamide intermediate. This pathway of reaction occurs at lower temperatures in comparison to that involving an acrylate intermediate, but its relative importance depends on the competitive reaction of the acrolein intermediate with the ammonia species and with catalyst lattice oxygens. NH3 coordinated on Lewis sites also inhibits the activation of propane differently from that absorbed on Brsurface reaction network in propane ammoxidation. 

Depending on the reaction temperature and reaction time, tetrahydroisoquinoline 357 afforded different mixtures of 1,2,3,4,11,11 a-hcxahydro-6//-pyrazino[ 1,2-3]isoquinolines 358-361 and tetracyclic compound 362 (Scheme 30) <2005JA16796>. Each of the individual diastereoisomers 358-361 could be transformed into the compound 362. z7r-3//,4a//-3-Phcnylpcrhydropyra/ino[ 1,2-7]isoquinoline-l,4-dione was prepared via automated parallel solid-phase synthesis on Kaiser oxime resin <1998BML2369>. l,2,3,5,6,7-Hexahydropyrido[l,2,3-r/f ]quinoxaline-2,5-dionc was obtained by catalytic hydrogenation of ethyl 3-(2-oxo-l,2,3,4-tetrahydro-5-quinoxalinyl)acrylate in the presence of TsOH over 5% Pd/C catalyst under 40 psi of hydrogen <1996JME4654>. 

This homologation of an oxime ether may have wider application for coupling of alkyl halides to other substrates such as acrylic esters (equation II). 

The oxime derived from 2-furfural has been used for the first time as an electron-rich 1-azadiene by Kusurkar and Bhosale (91TL3199) (Scheme 16). Thus, 2-furfuraldoxime 60 undergoes at 120°C [4 + 2] cycloaddition to acrylonitrile, acrylic acid esters, and maleic anhydride to give stereoiso-meric cycloadducts 61 and 62. The isomeric fused pyridines obtained were not separated, but dehydrogenated to the corresponding furo[2,3-c]pyridine N-oxide derivatives. 

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