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The literature has considered in detail the condensation reactions of aromatic aldehydes with 5H-furanones [1, 2]. Condensations of 5-substituted 3H-furanones have insufficient description jn the literature, and only relate to 5-aryl-and 5-methyl-3H-furan-2-ones [2, 3]; this is explained by the low availability of 5-alkyl-3H-furan-2-ones.On the basis of 4-oxoalkanoic acids, we obtained a series of 5-alkyl-3H-furan-2-ones, with the alkyl substituent from C3H 7 to C6H13, in yields up to 75% [4]. That allowed the study of their reaction with aldehydes of the benzene and furan series. All the indicated furanones (Ia-e) react by the crotonlc type of condensation at the position 3 of the heterocycle.The isolation of the 5-alkyl(aryl)-3-arylidene-3H-furan-2-ones (Ha-/) was accomplished in acetic anhydride in the presence of anhydrous sodium acetate. The synthesis of the compounds (II) is also possible by the treatment of 4-oxoalkanoic acids with the equimolecular amount of aldehydes in the presence of sodium acetate under conditions analogous to those described for the condensation of furanones.

An unusual direction was found in the condensation of cyclohexanone and its Mannich base, leading to the formation of previously unknown polycyclic spirohydrochromans. The structure of the compounds was confirmed by 13C NMR and mass spectrometry.Carbonyl-containing spirohydrochromans have become available as a result of the discovery of the ability of t~,flunsaturated ketones to enter into dimerization of the 1,4-addition type. Its characteristics and mechanism were discussed in detail in the review [1]. In [2][3][4] it was shown that the Mannich bases of cyclic ketones can act as synthons during their thermal decomposition, vacuum distillation [5][6][7], steam distillation [8], or acetolysis in acetic anhydride in the presence of sodium aceta.te [9, 10]. In view of the prospects concerning the scientific and applied aspects of compounds of this series we continued to develop optimum conditions of synthesis and investigate features of the transformations with regard to the existence of several reaction centers in the molecule.The methods that we proposed for the benzannellated analog The yield of the product amounted to 57-64%, depending on the conditions [boiling the base (II) in toluene in the presence of hydroquinone, boiling the methiodide of (II) in DMFA with 40% potassium hydroxide, or steam distillation of the hydrochloride of (II)].Compound (I) was oximated in order to confLrm the presence of the C------O group in the molecule. Here it was established that the direction of the reaction was determined by the order in which the reagents (NH2OH.HCI, KOH) were added. If hydroxylamine hydrochloride is added to a water-alcohol alkaline solution of the dimer of (I), the oxime (llI) is formed. Addition of the reagents in the reverse order leads to the formation of 2, 16-dioxatetracyclo[7.6.1.03,8.01,11]hexadecan_ 3-ol (IV) with a 64 % yield.

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On catalytic reduction of 2,6-diphenylpyrylium salts, hydrogenolysis occurs at the C-O bond with the formation of 1,5-diphenylpentanes. The principal direction of the hydrogenation of 9-phenyl-symoctahydroxanthylium tetrafluoroborate is the formation of a mixture of products of partial and complete reduction of the heterocycle. The structure of the substances obtained was established by IR and 13C NMR spectroscopy.Catalytic hydrogenation is a practically uninvestigated aspect of the well-studied chemistry of pyrylium salts. Up to the present time, only individual examples of similar reactions are known [1, 2]. We have studied the catalytic hydrogenation of pyrylium tetrafluoroborates (I)-(IV), differing in the number and nature of substituents, and their condensed analogs, the hydrochromylium (V) and (VI) and octahydroxanthylium (VII) tetrafluoroborates.Reaction was carried out in an autoclave in the temperature range 40-100~ and pressure 7-12 MPa on various catalysts. It was established that pyrylium salts (I)-(IV) react with rupture of the heterocycle and the formation in high yield (80-92%) of 1,5-diphenylpentanes (VIII)-(XI). The degree of substitution and the nature of the substituents (alkyl, aryl) have practically no influence on the yield of final product. A study has been made of the effect on the yield of hydrocarbon (X) of temperature, hydrogen pressure, and catalyst using 2,4,6-triphenylpyrylium tetrafluoroborate (III) as an example. At 40~ the yield of 1,3,5-triphenylpentane (X) was 68%, at 50~ it had increased to 80%, and remained practically unchanged on increasing the temperature to 100~ A further increase in temperature leads to hydrogenation of the benzene rings and the formation of a mixture of hydrocarbons separable with difficulty. On increasing the pressure from 7 to 10 MPa, the yield of product was increased by 20%. Of the catalysts investigated, Raney Ni, Pal/C, and Ni/Ru, the latter proved to be the most active (Table 1).The catalytic hydrogenation of 2-phenyl-5,6,7,8-tetrahydrochromylium (V) and 2,4-diphenyl-5,6,7,8-tetrahydrochromylium (VI) tetrafluoroborates leads to a complex mixture of products, which we failed to separate.On hydrogenating 9-phenyl-sym-octahydroxanthylium tetrafluoroborate (VII), the hydrocarbon (XII) was isolated in a yield of only 18% and the main direction of the reaction was the formation of the oxygen-containing heterocycles 9-phenyldecahydroxanthene (XIII) and 9-phenyl-dodecahydroxanthene (XIV), the combined yield of which was 51%.The reason for the different reaction direction seemingly follows from consideration of the various stabilities towards hydrogenolysis of the C-O bond of the saturated oxygen-containing heterocycles formed. The acid released on reduction of N.