Quinone, synthesis

Dithiaphosphorinanes, 1, 504-506 1,6-Dithia-6aA -selenapentalenes CNDO calculations, 6, 1052 PE spectra, 6, 1057 l,6aA -Dithia-6-selenapentalenes UV spectra, 6, 1056 7,10-Dithiasesquifulvalene-1,6-quinone synthesis, 6, 836... 

Dithiasesquifulvalene-1,2-quinone synthesis, 6, 836 2,3-Dithia-1 -silacyclopentene synthesis, 1, 577... 

This quinone synthesis was used to obtain the isoquinoline quinone 2, a unit of some saframycin antibiotics (equation I). 

Cannizzaro reaction, 2, 3 Carbanion, electrophilic amination, 72, 1 Carbenes, 13, 2 26, 2 28, 1 Carbene complexes in phenol and quinone synthesis, 70, 2... 

Quinone synthesis. Two laboratories12 have found that the adducts formed by addition of an aryl-, alkynyl-, or heteroaryllithium to a cyclobutenedione rearrange when heated (138-160°) to hydroquinones, which are usually isolated as the quinone after air or chemical oxidation. The rearrangement involves an interme-... 

Quinone synthesis (13, 97-98 209-210). Liebeskind1 has reviewed the use of organolithiums for preparation of benzoquinones from cyclobutenedione and of the reaction of benzocyclobutenediones with C1Co[P(C6Hj)3]3 to form either benzoquinones or naphthoquinones. These routes are particularly useful for regioselective synthesis of highly substituted quinones. 

Stannylquinones.1 The quinone synthesis based on addition of alkynyllithiums to substituted cyclobutenediones (13, 209-210, 284) can provide stannylquinones. Thus thermolysis of the alkynylcyclobutenol 1 with Bu3SnOCH3 results in rearrangement to the stannylquinone 2. As expected, these stannylquinones undergo palladium-catalyzed cross-coupling with organic halides (Stille reaction, 14, 35), particularly with allylic halides. 

Thallium trifluoroacetate has not enjoyed widespread use as a reagent for quinone synthesis, possibly because it is still a relatively new reagent but more probably because of its toxicity. One example of its use lies in the synthesis of metacyclophanes and related compounds as reported by Tashiro et al Thus the r-butylphenol (59) gave the bisquinone (61), while the phenol (60) afforded the monoquinone (62). An alternative and more practical synthesis of the bisquinone (61) for large scale work involved dealkylation to afford the bisphenol (63) which was then treated with sodium nitrite to give the bisoxime (64). Hydrolysis of the bisoxime did not give the quinone (61), but it could be obtained by zinc/acetic acid reduction of the bisoxime followed by oxidation with nitric acid (Scheme 13). 

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