4-isochromanone derivative

Heteroatoms can also participate in the ring expansion reaction mentioned above. For example, a hydroxyl methoxyallenylphthalan gave rise to a 4-isochromanone derivative. A hydroxymethoxyallenylisoindolinone afforded an isoquinolinedione derivative efficiently (Scheme 16.23) [27, 28]. 

Keto esters also react with salicylaldehyde to yield fused pyrylium salts. For instance ethyl 2-oxocyclohexanecarboxylate affords the tetrahydroxanthylium salt (645), whilst the isochromanone derivative (646) yields the tetracyclic molecule (647), which possesses the skeleton of the anthocyanidin, peltogynidine, isolated from the heartwood of Peltogyne porphyrocardia (Scheme 253) (58JCS3174). 

Classical photoinduced ultrafast Wolff rearrangement of 2-diazo-l-naphthoquinone (295) giving ketene intermediate (297) was investigated by theoretical calculations (Scheme 64). 5H-Furanone (302) was obtained by flow photochemical rearrangement of cyclobutenone (298) via ketene intermediate (301). On the other hand, thermal rearrangement of cyclobutenone (298) gave naphthalene derivative (300). Irradiation of 2-formyl cinnnamic ester derivatives (303) afforded unusual four membered cyclic ketones (304) and polycyclic isochromanone derivatives (305) (Scheme 65). ... 

Interestingly, the ort/io-alkenylation of aromatic aldehydes allowed the access to four-membered cyclic ketones and to polysubstituted isochromanone derivatives by an irradiation in benzene of the alkenylated product [(Eq. 62)] [144]. 

Chatteijee has synthesized a variety of yohimbine alkaloids utilizing 3-isochromanone derivatives as DE-ring precursors (Scheme 3.89) (140). For... 

Simple cyclobutanes do not readily undergo such reactions, but cyclobutenes do. Ben-zocyclobutene derivatives tend to open to give extremely reactive dienes, namely ortho-c]uin(xlimethanes (examples of syntheses see on p. 280, 281, and 297). Benzocyclobutenes and related compounds are obtained by high-temperature elimination reactions of bicyclic benzene derivatives such as 3-isochromanone (C.W. Spangler, 1973, 1976, 1977), or more conveniently in the laboratory, by Diels-Alder reactions (R.P. Thummel, 1974) or by cycliza-tions of silylated acetylenes with 1,5-hexadiynes in the presence of (cyclopentadienyl)dicarbo-nylcobalt (W.G, Aalbersberg, 1975 R.P. Thummel, 1980). 

The compounds covered in this section include dihydropyranones, tetrahydropyranones and their benzologues (dihydrocoumarins, chromanones and isochromanones). The area of greatest interest is undoubtedly the chromanones because of their relationship to a number of natural products and presumably also because of their ease of formation, stability and value as precursors of other heterocycles. Tetrahydropyran-2-ones comprise one of those nebulous areas of heterocyclic chemistry and usually feature in text books as 5-lactones under derivatives of hydroxy acids. 

The dilithio derivative of N-methyl-o-toluamide reacts with aromatic aldehydes and ketones to give hydroxyamides. Thermal cyclization affords 3-phenylisochroman-l-ones (64JOC3514). Spiroannelated isochromanones result when the organolithium compound reacts with fluorenone or alicyclic ketones. 

In connection with the anodic intramolecular coupling of 1-benzyltetrahydroiso-quinoline derivatives, the anodic oxidation of 4-(3,4-dimethoxybenzyl)-6,7-dimethoxy-isochromanone 15 has been studied rather extensively. The main product obtained from the isochromanone is a y-lactone, 7a,8-dihydro-3,10,ll-trimethoxy-2 H-phenanthro[9.8a, b]furan-2,7(5 H)-dione 16 13 ... 

As an alternative to our synthetic routes described so far, we also evaluated a more direct approach to the isochromanone fragment. As shown in Scheme 12, the concept to access 63 relied on a three-step, tandem process. The sequence was based on an iodocyclization of a suitable benzoic acid-derived alkene 64. After formation of putative iodonium intermediate 66... 

Two interesting and potentially useful syntheses of benzazepinones have appeared. In the first of these, isochromanone is converted into the acid (188) by fusion with KCN. ° The ester that is derived from this may be reduced,... 

In addition, the palladium-catalyzed C-H carbonylation is also useful to construct pyranone derivatives. In 2011, Yu s group reported a Pd(II)-catalyzed ortho-C-H carbonylation reaction of phenethyl alcohol derivatives to give 1-isochromanones by connecting the aryl moiety and alcohol with incorporated carbonyl group (Scheme 3.24) [49]. A wide range of functionahties such as methoxy, fluoro, chloro, and bromo are tolerated under the typical condition and afford various 1-isochromanones in moderate to good yields. The A-protected amino acids are supposed to reduce the rate of Pd(II) reduction in the presence of CO in this work. 

A related synthetic approach to yohimbine synthesis was utilized by Pandey and his coworkers (Scheme 3.91) (141,142). Thus, isochromanone 518 was converted to bromoester 519 which was then condensed with tryptamine to afford tetracyclic amide 520. Alternatively, 520 could be prepared by treatment of 518 with ammonia to provide 521 which was then AT-tryptophylated. Cyclization of 520 under standard conditions provided the dimethoxy-yohimbane derivative 522. 

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