Camphor quinone

The following oxidation of camphor to camphor-quinone illustrates the oxidising action of selenium dioxide, and readily gives a crystalline product. 

Starting material camphor quinone (Chapter 1, Section XI) and resulting in the formation of Horner s acid (5). 

Camphor Quinone Monotosylhydrazone To 22 g (0.133 mole of camphor quinone in 150 ml of chloroform is added 26.1 g (0.14 mole) of p-toluenesulfonylhydrazide in one batch. The reaction vessel is protected with a drying tube and fitted with a magnetic stirrer, and the mixture is stirred at room temperature for 24 hours. The monotosyl-hydrazone is not isolated. 

Camphor has been oxidised to camphor quinone which is an intermediate in the preparation of Homer s acid. 

In a study of the benzophenone sensitized photoreduction of camphor-quinone (16), Monroe and Weiner108-110 found that the quantum yield of photoreduction decreased from 0.386 to 0.087 as [16] increased from 0.003 to 0.20M. 

Scheme 34 shows the synthesis of the bc portion (336), which possessed three of the nine asymmetric centers present in cobyric acid. Retrosynthesis determined that (336) could be obtained, via sulfide contraction, from the two intermediates (337) and (338). Ring c was synthesized from (+)-camphor quinone (not shown). Ring b (337) was obtained from 8-methyl-j8-acetylacrylic acid (339), the two adjacent chiral centers being generated in the required relative orientation by a Diels-Alder cycloaddition with butadiene in the presence of tin(IV) chloride. Fractional crystallization served to resolve the diastereomeric a-phenethylamine salts derived from them, eventually affording the compound (340). Oxidation with chromic acid cleaved the double bond in (340) and one of the newly generated... 

Fig. 75 Catalytic cyclopropanation using a cobalt camphor quinone oximate complex...

In all tile above compounds tiie mercury appears to be in the mercuric state, no mercurous salts having been obtained by decomposition Muth halogen acids. The structural relationships of the mercury and iodine derivatives to camphor quinone is shown by the formula ... 

An efficient route to 7-oxocamphene involved as its key step the solvolytic rearrangement of 3,3-ethylenedioxyisobomyl tosylate (derived from camphor-quinone).621 Brief (3 min 0 °C) treatment (PCl5-CaC03) of borneol gave excellent yields of camphene hydrochloride longer reaction times gave bornyl chlorides.522... 

Very little information is available on reactions of unconjugated diones with olefins. The reaction of biacetyl with cyclohexene was first reported 79) in 1964 and repeated 20> in 1968 in both investigations no cycloadduct was observed. Preliminary results suggest 15) that camphor-quinone reacts with cyclohexene to form, in part, a keto-oxetane. 

Table 5.5 32.49. and used the auxiliary derived Irom camphor quinone to synthesi/.e the key hy-droxyben/.ylisoquinoline intermediates 19. 20. and 2.5 shown in Scheme 5.12 ].521. The absolute configuration of the new stereocenters of the addition products from ihese two auxiliaries (derived lrum. V-valine and l-/ -eaniphorqiiinonc oximei are opposite. In the schemes and accompany ing discussion below, the camphor-derived auxiliary is illustrated (Scheme 5.12), but die rest of the synthesis of all the alkaloids except eorlumine was actually executed on ihe enantiomer of that draw n. because it was done with the producl of addition using die valine-derived auxiliary. The references in die discussion refer to the relevant papers for each step. 

Also, all the -situated hydrogen atoms of ketones are readily replaceable by deuterium in an aqueous alkaline medium, since these atoms take part one after the other in the reversible keto-enol tautomerism. This applies, for instance, to the four -positions of cyclohexanone and to the one of 2,2,6-tri-methylcyclohexanone, whereas no exchange occurs in camphor or camphor-quinone which cannot enolize owing to the particular stereochemistry of the molecules.90 Open-chain ketones and also steroidal ketones91 that are not subject to this limitation are often used for exchange reactions. The following description of the preparation of [D6]acetone illustrates the point 29... 

CYCLOPROPANATION Bis[(-)-camphor-quinone-a-dioximato] cobalt(II) hydrate. Diethylzinc-Methylene iodide. Rhodium(II) caiboxylates. 

In conjunction with hydrogen donors such as dimethylaniline and triethyla-mine, benzils and various quinones, such as anthraquinone, 9,10-phenanthrene quinone, and camphor quinone (see Chart 10.4), can be used as visible-light-sensitive photoinitiators [8]. Some of these compounds are used to cure dental restorative systems (see Section 11.3). Another application concerns the curing of waterborne pigmented latex paints, which do not contain volatile organic compounds (VOCs) [48]. 

Photoinitiator systems from hydrogen abstraction or electron transfer usually contain two components a photoinitiator (typically an aromatic ketone) and a co-initiator with a weak covalent bond. Some examples for this system include benzophenones (1), thioxanthones (2), benzyls (3), camphor-quinones (CQs) (4), and ketocoumarins (5), which can be used in the presence of H donors (alcohols, THE, and thiols) or electron donors (such as amines) (Table 2). One of the drawbacks of photoinitiation requiring electron transfer is back electron transfer that limits their practical utility. For this reason, the acidity of the C-H bond of the co-initiator is of great importance. A few initiators are also able to undergo cationic and radical photoinitiation such as iodium and sodium salts and arene complexes. ... 

Treatment of cobalt(n) chloride in alkaline aqueous methanol with (+)-camphor-quinone-a-dioxime under nitrogen gives the air-sensitive complex (39) which is an... 

In an interesting paper it is revealed that di-t-butylnitroxide (DTBN) radical induces upheld contact shifts for the X-H proton donor molecules and conforma-tionally dependent downfield shifts for C—H protons in accordance with the W-rule. Methyl protons in close spatial contact with the N-H or O-H proton donor groups exhibit marked DTBN-induced downfield pseudo-contact shifts. The origin of these effects and their potential uses are discussed. Proton shifts for various monoterpenes e.g. camphor, camphor quinone, and pinocarvone) in hexafiuorobenzene are compared with the shifts obtained in other, more conventional, solvents. Unusually large couplings between the OH and adjacent CH protons have been observed for extremely pure samples of syn- and anrt-7-hydroxynorbomene in particular solvents. " The simplification in the spectra of these compounds, of 7-hydroxynor-bornadiene, and of the catalytically deuteriated (exo-addition) derivatives, with the aid of Eu(dpm)3 and Eu(fod)3 is reported in a companion communication. ... 

Amines, such as dimethylaniline and triethylamine, are also used as coinitiators for free-radical polymerizations [154,155]. In these cases, initiating radicals are supposedly generated through exciplex formation, followed by proton transfer. The low order of toxicity of camphor quinone and its curability by visible light makes such systems particularly useful for dental applications [152,156,157]. Noteworthy is that the reactivity is relatively low, owing to a comparably low efficiency in hydrogen-abstraction reactions. This circumstance has prevented the use of quinones in other applications. 

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