Phthaloylmetal complex

Benzocyclobutenedione 57 is transformed to the phthaloylmetal complex 58 by treatment with Fe(CO)5, RhCl(PPh3)3, and CoCl(PPh3)3. The phthaloyliron complex 58 (M=Fe) reacts with alkynes, and subsequent acidification under air then gives the naphthoquinone 59. The cyclization of the phthaloyl-cobalt 58 (M=Co) with alkynes requires AgBF4-activation [32]. (Scheme 22)... 

Pyranonaphthoquinones. The reaction of phthaloylmetal complexes with alkynes to give naphthoquinones (10, 221-222) has been extended to a synthesis of pyrano-naphthoquinones. An intramolecular version of the reaction is used to control the regio-selectivity. The method is outlined in Scheme (1) for a synthesis of nanaomycin (6) and the cw-epimer (7). 

Cyclobuten-l,2-diones underwent oxidative addition to various low-valent metals such as Pt(PPli3) and RhCl(PPh3)3 with site-selective cleavage of the C(arene)-C(carbonyl) bond (Scheme 1.16) [24]. The rhodium complex subsequently underwent rearrangement to furnish the phthaloylmetal complexes. 

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