The Camphor Group

Camphor.—This substance, as shown by the synthesis carried out by Romppa,1 has certainly the formula proposed by Bredt  

Being a ketone it can be reduced to the secondary alcohol borneol  

This reduction has been carried out electrolytically by Tafel. and Schmitz2 in sulphuric-acid solution at mercury catnodes. They obtain thus about 45 per cent, of the theoretically possible yield, with a maximum current consumption of 38 per cent. At lead cathodes no satisfactory reduction can be effected. Camphoric Acid, 

Brown and Walker3 also electroylzed (see p. 102) the. sodium-ethyl salt of camphoric acid and obtained two esters which they were able to separate by means of fractional dis- 

A ketonic acid, CsH O-COOH, melting-point 228°, is also found as an additional product of the electrolysis of potassium 

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The enantioselective addition of diethylzinc to aromatic aldehydes has been performed in the presence of an IV-sulfonylated amino alcohol-Ti(0-/-Pr)4 catalytic system.113 In the presence of (42), excellent enantioselectivities (up to 94% ee) have been obtained. The study revealed that the steric bulk of the camphor group does not affect the stereocontrol. 

When camphor (I) is heated with selenium dioxide in acetic acid, the methylene group next to the carbonyl group is oxidised also to a carbonyl group, to form camphorquinone (II). Note that the compound (II) is not a true quinone but a 1,2-diketone ... 

Comparison of Table 5.4 and 5.7 allows the prediction that aromatic oils will be plasticisers for natural rubber, that dibutyl phthalate will plasticise poly(methyl methacrylate), that tritolyl phosphate will plasticise nitrile rubbers, that dibenzyl ether will plasticise poly(vinylidene chloride) and that dimethyl phthalate will plasticise cellulose diacetate. These predictions are found to be correct. What is not predictable is that camphor should be an effective plasticiser for cellulose nitrate. It would seem that this crystalline material, which has to be dispersed into the polymer with the aid of liquids such as ethyl alcohol, is only compatible with the polymer because of some specific interaction between the carbonyl group present in the camphor with some group in the cellulose nitrate. 

Camphor is the ketone of the alcohol borneol and forms a number of well-characterised crystalline derivatives. Amongst these are the semi-carbazone, the phenylhydrazide, and the oxime, all characteristic of bodies containing the. CO. group. -The semi-carbazone,... 

The most important group of derivatives for the amino function (Fig. 7-4) is the carbamate group, which can be formed by reactions with acids, acid chlorides or acid anhydrides. A series of chlorides as 2-chloroisovalerylchloride [1], chrysanthe-moylchloride [2] and especially chloride compounds of terpene derivatives (cam-phanic acid chloride [3], camphor-10-sulfonyl chloride [4]) are used. The a-methoxy-a-trifluoromethylphenylacetic acid or the corresponding acid chloride introduced by Mosher in the 1970s are very useful reagents for the derivatization of amines and alcohols [5]. 

Yan s group has used the camphor-based chiral thioamide 62 in asymmetric Darzens reactions (Scheme 1.21) [32]. The addition of the titanium enolate of 62 to... 

In contrast to the extraordinarily high preference for endo attack observed with camphor (1), nucleophilic additions of organolithium and Grignard reagents to norcamphor (3) proceed with exclusive attack of the nucleophile from the exo face of the carbonyl group. 

Several methods for asymmetric C —C bond formation have been developed based on the 1,4-addition of chiral nonracemic azaenolates derived from optically active imines or enamines. These methods are closely related to the Enders and Schollkopf procedures. A notable advantage of all these methods is the ready removal of the auxiliary group. Two types of auxiliaries were generally used to prepare the Michael donor chiral ketones, such as camphor or 2-hydroxy-3-pinanone chiral amines, in particular 1-phenylethanamine, and amino alcohol and amino acid derivatives. 

Two S/P ligands derived from camphor, CamPHOS and MeCamPHOS were also developed by these authors for the diastereoselective coordination to alkyne-hexacarbonyldicobalt complexes (Scheme 10.68). These two ligands were converted in good yields into their borane-protected forms. The influence of the alkyne group (R) on their coordination to dicobalt-hexacarbonyl-alkyne complexes was evaluated. It was shown that MeCamPHOS ligand provided a... 

There are two types of electron transport those involving flavoproteins and iron-sulfur proteins, and those requiring only flavoproteins. The X-ray crystal structure of the soluble cytochrome P450 from Pseudomonas putida grown on camphor (P-450-CAM) has been determined (Poulos et ah, 1985), as have several others. The haem group is deeply embedded in the hydrophobic interior of the protein, and the identity of the proximal haem iron ligand, based on earlier spectroscopic studies (Mason et ah, 1965) is confirmed as a specific cysteine residue. 

It is also possible to carry out a substrate-controlled reaction with aldehydes in an asymmetric way by starting with an acetylene bearing an optically active ester group, as shown in Eq. 9.8 [22]. The titanium—acetylene complexes derived from silyl propiolates having a camphor-derived auxiliary react with aldehydes with excellent diastereoselectivity. The reaction thus offers a convenient entry to optically active Baylis—Hillman-type allyl alcohols bearing a substituent (3 to the acrylate group, which have hitherto proved difficult to prepare by the Baylis—Hillman reaction itself. 

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