Nitroso chlorides

Sometimes, on account of the difiiculty in preparing the nitroso-chloride from a highly active o-pinene, it is necessary to examine the oxidation products before it is possible to come definitely to a conclusion as to the presence or absence of the hydrocarbon. Pinene yields numerous acids as the result of oxidising processes, so that the method of preparing the product to be examined must be rigidly adhei ed to if useful results are to be obtained. The terpene is transformed into pinonic acid, CjoHj Og, in the following manner A solution of 233... 

Mojjo 1-4641. It does not form a crystalline hydrochloride or nitroso-chloride. Zelinsky assumes that a-pinene first absorbs hydrogen, with the formation of hydropinene, and that isopinene results from the latter, according to the following formulae —... 

Terp-caryophyllene and Zim-caryophyllene can be converted the one into the other by the preparation of their nitrosites or their nitroso-chlorides, and subsequent regeneration of the sesquiterpene. They also both yield the same hydrochloride, melting at 69°. 

Further details of the photoaddition of N-nitrosopiperidine to a-pinene have been published.The claim of a-fenchen-6-one oxime formation (Vol. 7, p. 43) has been retracted the product is optically active carvone oxime. The stereochemistry and conformations of amino-oximes derived from a-pinene nitroso-chloride have been examined. ... 

The mechanism and the stereoselectivity of the reaction7,11-13 are affected not only by the structure of the alkene, but also by the method of preparing the nitroso chloride and by the solvent. Different mechanisms may be followed two-stage anti addition (NO Cle), particularly in polar solvents such as sulfur dioxide, or syn molecular addition via a four-centered cyclic transition state, favored in low polarity solvents such as dichloromethane and carbon tetrachloride. 

The simple (cis/trans) diastereoselectivity and the face selectivity are dependent on the substitution pattern of the cyclohexene ring, e.g., 6-8, prepared from 8,9-dihydrolimonene4,39, sylvestrene43, and 3-carene43,15°, respectively. In solution the nitroso chloride dimer 8 is in equilibrium with the oxime 943. 

Racemic a-pinene nitroso chloride dimer 10 was obtained from optically impure a-pinene by precipitation from the reaction mixture, whereas optically active 10 was obtained in very low yield (< 5 %) from the mother liquor due to its greater solubility44. Even in more recent reports, the configuration of 10 has not been rigorously determined39,150. 

The nitroso chlorides prepared from limonene, sylvestrene, 3-carene, and a-pincnc have been converted to a-amino oximes by treatment with aliphatic and aromatic amines with unspecified yields39,42,43-15°-151. The configuration of the products was determined by NMR spectroscopy, molecular mechanics calculations and X-ray crystallographic analysis 50, in some cases reversing the configuration previously assigned. The stereochemical outcome of the reaction is rationalized by attack of the amine from the least hindered side of the intermediate nitroso alkene. 

Nitroso, azoxy and azo groups are also reduced under the conditions used to effect the hydrogenation of nitro compounds. Nitroso compounds form the amine with about the same ease as is observed with the corresponding nitro compound. a-Nitroso-chlorides are hydrogenated to oximes over platinum if the reaction is stopped when the color disappears (Eqn. 19.30). No other catalyst is effective for this reaction, which is also superior to all chemical reduction methods. The use of other catalysts, as well as further hydrogenation over platinum, results in amine formation. ... 

Meinwald and co-workers investigated the stereochemistry of the dimeric nitroso chlorides from norbornene (1) and norbornadiene and concluded that the products have the exo-ds stereochemistry as in (3). Lack of rearrangement, cis... 

An interesting reaction of nitroso chlorides derived from tetrasubstituted olefins described by Closs is reduction to the chloroamino derivative and cyclization by base to an aziridine. The sequence is not applicable to less fully substituted olefins because the nitroso chloride decomposes during attempted reduction. 

Pummerer reported that the nitroso chloride (2) on refluxing with pyridine affords the a,j8-unsaturated oxime (3). 

A li isubstituted olefin is unsymmetrical, and nitrosyl chloride invariably adds to give the nitroso chloride in which the chlorine atom is attached to the more highly substituted carbon atom, as in (2). Unlike (1), however, the product is colorless. The interpretation now generally accepted is that the less hindered nitroso compound (2) dimerizes to the more stable form (3), which is colorless. Heating some-... 

Allhtnigh the rate of reaction of olefins with nitrosyl chloride decreases with ilecreiising number of alkyl substituents, crystalline nitroso chlorides (dimeric) have been obtained even from ethylene and propylene. ... 

Fraction 160" to 165" had a pronounced terpene odour. Specific gravity 0 8695 at 15" optical rotation an = - 15 10. The nitroso-chloride of the melting-point 10 to 103", and the nitrol benzylamine melting at 122 to 123", obtained from the former, proved the presence of pinene. 

Pig. 39.—Photomicrograph of crystals from lemon oil (x 100). a, b, Limonene nitroso-chloride crystals from lemon oil c, Limonene and pinene nitroso-chloride crystals from a lemon oil mixed with 5 per cent, of turpentine d Pinene nitroso-chloride crystals from turpentine. 

In spite of the fact that a double or triple bond is very reactive, there is no general method known for the preparation of solid derivatives. A series of unsaturated hydrocarbons (especially terpenes) can be identified by conversion them to nitroso chlorides (16). Crystalline derivatives are often obtained by addition of HCl or HBr ... 

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