developed in Part I11 (J., 1960, 3117) has been extended to the synthesis of flavani and their derivatives from a series of polyhydroxyphenols. From some a number of a-and y-pyronoflavans have been prepared.IN reviewing possible routes for the synthesis of dracorubin-type compounds we were attracted by the idea of employing a residue of type (I), containing the flavan system already formed, rather than to attempt the construction of this unit on to a flavylium compound, more especially because of the experimental limitations encountered in the synthesis of the flavan system (Part 111, J., 1950, 3117). As a preliminary to exploring this route to the dracorubin system the general procedure developed in Part I11 (Zoc. cit.) has been extended to the svnthesis of a series of flavans from resorcinol, orcinol, quinol, hydroxyquinol, and keto-derivatives it (111), and (IV). R phloroglucinil, and pyrogallol. Further, from some of the formylhas been possible to obtain, e.g., cc-and y-pyronoflavans, types (11),In these studies there emerged several experimental features of general interest which may be noted. (a) Most parent flavans are extremely dficult to crystallise and several of the hydroxy-compounds are readily susceptible to aerial oxidation. (b) The flavan oxygen system is sensitive to acidic reagents above room temperature and attempts to demethylate O-methylflavans by the standard methods are uniformly unsuccessful. Further, whilst, e.g., 8-formyl-7-hydroxyflavan (I ; R = CHO) readily reacted with acetophenone in ethereal hydrogen chloride, the resulting flavylium salt was resinous and could not be purified. (c) With chromic anhydride O-methylflavans furnish low yields of the corresponding flavanones, thus providing a method of detecting the flavan system. EXPERIMENTAL 7-HydroxyfEavan (I ; R = H).-A solution of 7-hydroxyflavanone (Ellison, J. , 1927, 1722) ( 1 g.) in acetic acid (40 ml.), containing concentrated hydrochloric acid ( 5 ml.), was reduced with zinc amalgam (from 10 g . of zinc dust) at room temperature and 24 hr. later the solution was decanted and diluted with water. Purification of the resulting precipitate from light petroleum (b. p. 6O--SO0), containing a small amount of methanol, yielded 7-hydroxyfavan (0.7 g.) in prisms, m. p. 71", readily soluble in 2~-aqueous sodium hydroxide and having a negative ferric reaction (Found : C, 79.6; H, 6.3. Cl5Hl4O2 requires C, 79.6; H, 6.2%).
7-Hydroxy-8-rnetlzyZ~7avan (I ; R = Me) .-(a) Prepared by Gattermann's method from 7-hydroxyflavan (1 g.), hydrogen cyanide ( 5 ml.), and zinc chloride (0.5 g.) in ethereal hydrogen *