Hetero-Diels–Alder reaction of halogenated quinones with a polygodial-derived azadiene

(-)-Shikimic Acid as a Chiral Building Block for the Synthesis of New Cytotoxic 6-Aza-Analogues of Angucyclinones

“…The chemical structure of 19c was unequivocally established from the crystallographic data, as shown in Section 2.2 . Considering these results, and other reports that show that when some haloquinones are used in Diels-Alder reaction, several oxidation processes are favourable on the adducts due to their more reactive properties [ 37 ]. Based on these antecedents, we proposed an eventual mechanism to explain the formation of 19a – c and 20 , which is outlined in Scheme 3 .…”

“…To obtain 6,8-diaza-anguciclyne derivatives using the same strategy, halogenated-naphthoquinone derivatives ( 18a – b ) were required to obtain only the desired regioisomer due to the orientation effect of the halogen atom on the quinone [ 37 , 38 ] and to the increase of the reactivity of dienophile. The only change for the condition reactions for this cycloaddition was the addition of NaHCO 3 , which is necessary when a haloquinone is used [ 37 , 39 ]. For these cases, the reaction times were less than the described above, decreasing from three days to five hours.…”

Preliminary Studies on the Synthesis of (–)-Shikimic Acid Based 1,2,3,4-Tetrahydrobenzo[b]phenanthridine-7,12-diones

“…12 A useful precedent was the efficient, regioselective synthesis of the benzo[b]phenantridine skeleton of phenantroviridin by a sequence consisting of a cycloaddition of juglone and 3-bromojuglone with a proper innerouter azadiene, followed by a spontaneous aromatization involving the elimination of hydrogen halides and dimethylamine from the resulting cycloadducts. 8,13,14 Herein we report the first examples of aza-Diels-Alder cycloadditions of a shikimic acid derived N,N-dimethylhydrazone 6 with quinones (Scheme 2).…”

N,N-Dialkylhydrazones in Organic Synthesis. From Simple N,N-Dimethylhydrazones to Supported Chiral Auxiliaries

“…ij][2,7]naphthyridin-7-one(275), an analogue of kuanoniamine A (marine alkaloid), 217 a regioisomer of the marine alkaloid meridine 9-hydroxybenzo[b]-pyrido[4,3,2-de](1,10)-phenanthrolin-8-one(276),218 diazaquinomycin A (277),219 dihydrofuroquinolinedione derivative 278, 220 substituted 1,8-diaza-9,10-anthraquinone 279,221 1,5-diazaanthraquinone derivatives 280,222,223 and tetracyclic compound 281 224. The Diels-Alder reaction of 282 (Scheme 53) was the key transformation in the synthesis of analogues of the marine pyridoacridines meridine and ascididemin.…”