Phosphorus oxychloride adducts

This method is very useful for the construction of 1-substituted 3,4-dihydroisoquinolines, which if necessary can be oxidized to isoquinolines. A P-phenylethylamine (l-amino-2-phenylethane) is the starting material, and this is usually preformed by reacting an aromatic aldehyde with nitromethane in the presence of sodium methoxide, and allowing the adduct to eliminate methanol and give a P-nitrostyrene (l-nitro-2-phenylethene) (Scheme 3.17). This product is then reduced to the p-phenylethylamine, commonly by the action of lithium aluminium hydride. Once prepared, the p-phenylethylamine is reacted with an acyl chloride and a base to give the corresponding amide (R = H) and then this is cyclized to a 3,4-dihydro-isoquinoline by treatment with either phosphorus pentoxide or phosphorus oxychloride (Scheme 3.18). Finally, aromatization is accomplished by heating the 3,4-dihydroisoquinoline over palladium on charcoal. 

A method for making benzonitrile by dehydrogenation of the Diels-Alder adduct of butadiene and acrylonitrile also has been described (79). Benzonitrile also can be made on a small scale by the dehydration of benzamide in an inert solvent with phosphorus oxychloride or benzenesulfonyl chloride and an organic amine (80,81). 

For the carbonyl component in reactions with l-aminoanthraquinones 319, one can use methyl and methylene ketones as well as adducts between A.M-dimethylacetamide and phosphorus oxychloride, which leads to py-... 

Molecular halogens react with the thiones to give initially 1 1 adducts, formulated probably as 3-halothio-l,2-dithiolylium halides (42). For chlorine, these types convert to 3-chloro-1,2-dithiolylium salts (35a X = C1) (81AHC(23)i5l, 76PS(i)i85). Other more easily controlled halogen sources may be used, including thionyl chloride, oxalyl chloride, sulfur chloride and phosphorus oxychloride (70LA(742)103). A possible pathway for reaction with oxalyl chloride is shown in Scheme 19. 

The dehydrating agent in the case of the guanidines is HFA itself phosphorus oxychloride has to be used to effect ring closure in the case of the amidines (52). An intermediate 1 1 adduct 111 can be isolated, which, in addition to the formation of llOd and IlOe, on dehydration reacts with the aromatic system to yield 3,4-dihydrochinazolines 112 (52). 

Phosphorus oxychloride may be used in place of zinc chloride, and this is recommended for cases where the latter has not sufficient condensing action owing to the low solubility of its amine adduct.884 Boron trifluoride etherate was found to be a particularly active catalyst for condensation of 9-fluorenone with aromatic amines.885... 

A kinetic study of the nitrosation, at C-3, of the indolizine (764) and of its nitration, which occurs at C-4, has been presented.The reaction of diethyl azodicarboxylate with 2-methylindolizine yields a mixture of the mono-adduct (765 R = H) and the di-adduct [765 R = N(C02Et)NHC02Et]. "" The novel zwitterion (767 Ar = P-CIC6H4) is formed by the action of chlorobenzene-p-sulphonyl azide on the cyclohexenoindolizine (766). A stable carbo-selenaldehyde (768) has been obtained by treatment of 2,7-dimethylindolizine with the dimethylformamide-phosphorus oxychloride complex followed by sodium hydrogen selenide. ... 

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