A-Bromo camphor

The 1-dichloro-d-bromo-camphor sulphonie salts are the least soluble. The colour of these optically active derivatives is the same as that of the racemic salts. 1-Dichloro-diethylenediamino-chromie d-a-bromo-camphor sulphonate, [Cren2Cl2]SO3C10H14OBr, forms small, shining violet crystals, and has specific rotation [molecular rotation of [M]D + 176-9°. Solutions of both isomers are rapidly raeemised. 

Phenylbenzylmethylallylarsonium iodide, (C H5)(CgH5.CH2) (CH3)(CgH5)AsI, forms colourless crystals, M.pt. 100° C. Its d-a-bromo-camphor-TT-sulphonate crystallises in prisms, M.pt. 189° C., and cannot be resolved. 

Since Werner s pioneering work on optical activity in complex inorganic compounds there have been many important developments in the field. One of the more interesting of these is known as the Pfeiffer effect which is a change in the optical rotation of a solution of an optically active substance e,g, ammonium d-a-bromo-camphor-T-sulfonate) upon the addition of solutions of racemic mixtures of certain coordination compounds (e,g, D,L-[Zn o-phen)z](NOz)2, where o-phen = ortho-phenan-throline). Not all combinations of complexes, optically active environments and solvents show the effect, however, and this work attempts to apply optical rotatory dispersion techniques to the problem, as well as to determine whether solvents other than water may be used without quenching the effect. Further, the question of whether systems containing metal ions, ligands, and optically active environments other than those already used will show the effect has been studied also,... 

Retusamine, G19H25NO7 (mp 174.5° [ajp +13°), isolated by Gul-venor and Smith (77), was shown by Wunderlich (64) from X-ray diffraction of a single crystal of its a-bromo-( + )-camphor-frans-7r-sulfonate monohydrate to have structure GLX. The free base, however, is best... 

In 1931, Pfeiffer and Quehl observed that the optical rotation of a solution of an optically active compound (e.g., ammonium ti-a-bromo-camphor-TT-sulfonate, hereinafter called an environment compound) changes significantly upon the addition of solutions of racemic mixtures of certain coordination compounds (e.g., D,L-[Ni(o-phen)3]Cl2). Brasted and his students, and Dwyer and his co-workers have studied this effect in some detail with particular reference to the source and nature of the effect. Kirschner and his co-workers have also studied the effect and have found considerable evidence in support of the mechanism for this effect described by Dwyer and his co-workers. Kirschner and Magnell" have developed quantitative expressions for the rotation change due to the Pfeiffer effect, and have defined a positive Pfeiffer rotation as an enhancement of optical... 

In recent years, several modifications of the Darzens condensation have been reported. Similar to the aldol reaction, the majority of the work reported has been directed toward diastereo- and enantioselective processes. In fact, when the aldol reaction is highly stereoselective, or when the aldol product can be isolated, useful quantities of the required glycidic ester can be obtained. Recent reports have demonstrated that diastereomeric enolate components can provide stereoselectivity in the reaction examples include the camphor-derived substrate 26, in situ generated a-bromo-A -... 

Camphor reduction, a-bromo ketone to ketone, 127 Carbenium ions ... 

Photolysis of the blue solid (+)-10-bromo-2-chloro-2-nitrosocamphane (270) with red light produces two nitroxide radicals 271 and 272 and 10-bromo camphor 273, 10-bromo-2-chloro-2-nitro camphane 274 in addition to some minor products (equation 122). A complex reaction mechanism has been proposed144. 

X-Ray diffraction studies of ( )-carbocamphenilone," of (-)-camphene-8-carboxylic acid," and of a number of Money s brominated camphor derivatives (Vol. 6, p. 39 Vol. 7, p. 40) have been published they include 8-bromo-camphor," l,7-dibromo-3,3,4-trimethylnorbornan-2-one, l,7-dibromo-4-... 

The resolution was carried out by means of d-bromo-camphor-sulphonie acid. The salts of the bromo-series are more easily resolved on account of the great difference between the isomeric d-bromo-camphor sulphonates. In both series the d-bromo-eamphor sulphonate of the d-isomer is more sparingly soluble. These active compounds are very stable, and aqueous solutions of the bromides of the bromo-ammine series may be kept for a considerable time at ordinary temperatures, and even on heating to boiling racemisation does not occur. If the bromine in the complex be removed by means of silver nitrate activity... 

In 1913 Werner 2 described a new series of optically active cobalt compounds containing two asymmetric cobalt atoms in the molecule, the tetraethylenediamino-/i-amino-nitro-dicobaltic salts. The resolution is effected by treating tetraethylencdiamino - /x - amino - nitro-dicobaltic bromide with silver d-bromo-camphor sulphonate and fractionally crystallising the product. 

Three different d-bromo-camphor sulphonates are obtained, namely, (1) an inactive crystalline salt containing eight molecules of water of hydration, from which a series of hevo-salts can be prepared (2) an active crystalline form with seven molecules of water of hydration, yielding a series of meso-salts and (3) another active form with six molecules of hydration, yielding a series of dextro-salts. 

The nitrate is transformed into the bromide, and this is then treated with active silver bromo-camphor sulphonate. A dark green solution is formed, and a difficultly soluble bromo-camphor sulphonate mixed with silver salt. This mixture is extracted with hot water and the solution so obtained fractionally crystallised. The resolution is tedious and the yield is not good. 

The bromo-camphor sulphonate, [Ir en2(NO2)2][d-C10H14O4BrS], is prepared by treating the iodide with silver bromo-camphor sulphonate. It separates as a vitreous mass. 

The Pfeiffer Effect (1) is defined as the change in optical rotation of an optically active system (usually a solution of one enantiomer of an optically active compound, called the "environment substance", dissolved in an optically inactive solvent) upon the addition of a racemic mixture of a dissymmetric, optically labile coordination compound. Much work has been done on this Effect (2 - 8) and several mechanisms have been proposed to explain it, which are described in a review by Schipper (2). It is of interest to note that the Effect can occur with racemic mixtures of certain optically labile complex cations (e.g., D.L-[Zn(o-phen)3]2+) whether the environment substance is anionic (d- -bromo-camphor- -sulfonate), neutral (levo-nicotine), or cationic (d-cinchoninium), The most frequently used solvent for the Pfeiffer Effect is water (10), although the Effect is known to occur in other solvents as well (l.it.6). 

This conclusion has been confirmed by a total synthesis of macronecine (7), which involves successive reductions of the racemic pyrrolizidine ester (8) by zinc and acetic acid, followed by lithium aluminium hydride. Resolution was achieved via the a-bromo-D-camphor-n-sulphonate salts. The conclusion concerning the relative stereochemistry in macronecine was substantiated by the preparation of the other three racemates having the same gross structure as macronecine, and a detailed comparison of their n.m.r. spectra. In consequence of this work, the complete structure of macrophylline is as given in (9). ... 

A. G. Giumanini, L. Caglioti, and W. Nardini, Reaction of 3-bromo camphor with pheny lhydrazine, Bull. Chem. Soc. Jpn., 46 (1973) 3319-3320. 

Spath and Leithe (225) reinvestigated the resolution of tetrahydroberberrubine with a-bromo-d-camphor-TT-sulfonic acid and from the first fraction obtained a base having [a] d +52°. This when fractionally crystallized from a variety of solvents ultimately yielded the d-base (m.p. 195-196°) of [a] +303° (chloroform) and [q ]b +298° (ethanol). The Z-base was similarly obtained from the first fractionation and had [aJi —304° (chloroform). These results were taken to indicate that Kitasato s conclusions Avere in error. 

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