N,N‐Dimethylaminobenzotriazolylcarbene (5) reacted with phenyl isocyanate in a [1+2+2] cycloaddition and then with nucleophiles to generate various hydantoins 10 in a one‐pot procedure. It was also found that this novel carbene reacted with trans‐dibenzoylethylene (11) in a [1+4] cycloaddition, generating 2‐dimethylamino‐3‐benzoyl‐5‐phenylfuran (13) and 2‐phenyl‐3‐[benzotriazol‐1‐yl]‐4‐benzoylfuran (14) whose structures were confirmed by 1H‐13C long range correlations as well as the structure of furan 14 being confirmed by X‐ray crystallography.

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Heterodiene cycloadditions of 3-formylchromone 2 to a series of ketene acetals 1 derived from C2 symmetric 1,2-diarylethane-1,2-diols are diastereoselective. From (S,S)-1,2-di(o-t0lyl)ethane-1,2-diol 6c the major cycloadduct 3c was isolated by crystallisation and transformed by acid-catalysed methanolysis into (S)methyl 4-oxo-3,4-dihydro-2H-1 -benzopyran-2-ylacetate 5, together with the original 1,2-diol6c which could be recycled. The structures of two cyclic carbonates 22a and 22c were determined by X-ray diffraction and used as models in seeking a mechanistic rationale for the stereoselective cycloadditions of the analogous ketene acetals l a and lc.

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The pigments of immature Polyporus hisflidus fruits have as main component the styrylpyrone derivative (IV) (hispidin), which during ripening is oxidised enzymically 'to lignin-like material. The structure-determination and synthesis of trimethylhispidin are described, with syntheses of some related compounds. IN Britain, Polyporus hispidm (Bull.) Fr. is a common cause of white rot in hedgerow ash-trees ; its conspicuous bracket-shaped fruits appear annually and when immature the red-brown flesh affords much ethanol-soluble pigment. The main constituent of this pigment we have named hispidin, and its structure was announced, without details, in 1959.l Edwards et al. recently described independent work on the same compound; here we present details of our own work, leading to similar conclusions, with an assessment of the function of pigments of this type.After somewhat tedious purification, hispidin was crystallised as the yellow hydrate, C13H100S,H20, which with diazomethane or dimethyl sulphate gives a high yield of tri-0methylhispidin, C13H,02(OMe),. Since this derivative is conveniently obtained directly from the crude (methoxyl-free) pigment it formed the basis of our structural study.Tri-O-methylhispidin is neutral, shows no quinonoid or ketone properties, and gives none of the colour reactions for the main types of natural pigment. The infrared spectrum suggested the presence of an ester-carbonyl group (probably in an enol-lactone) and a 1,2,4-substituted benzene ring, but no hydroxyl group; as the parent phenol gives a strong green ferric chloride reaction a 4-substituted catechol nucleus seemed probable, The ultraviolet absorption ( A, , at 250 and 367 mp with only weak intervening absorption) resembles that of hispidin itself but differs markedly from those of any common natural pigments. Mild hydrogenation gives a colourless dihydro-derivative ( A, , 223 and 280 mp) but further hydrogenation occurs easily. Oxidation with neutral permanganate gives veratric acid, and treatment with hot aqueous alkali gives 3,4-dimethoxycinnamic acid.Consideration of biogenetically plausible structures for a C13 enol-lactone which would give a cinnamic acid hydrolytically led us to compare tri-O-methylhispidin with yangonin, a yellow styrylpyrone isolated by Borsche and Gerhardt from " kawa," Piper methysticum. Dr. B. K. Blount very kindly supplied us with yangonin and we found the ultraviolet and infrared spectra strikingly similar to those of tri-0-methylhispidin. Having first shown * that yangonin is unambiguously 4-methoxy-6-4'-methoxystyryl-2-pyrone, we tested the analogous formulation of tri-0-met hylhispidin, 4-methoxy-6-(3,4-dimet hoxy-styry1)-2-pyrone (I) by applying the degradation sequence used by Borsche for y a n g ~n i n , ~ viz., hydrolysis to the diketo-acid (11) and decarboxylation to the diketone (111), which we found identical with synthetic material. The formula (I) was then confirmed by synthesis from the or-pyrone isomer of " triacetic acid lactone methyl ether " (cf. ref. 4) and verat raldehyde.The...