quinazolinone annelation of 3-oxopyrrolo[3,4-b]quinoline (124) has been reported by Ganesan et al. in 1998 [285]. They prepared required amide 124 by Danishefsky procedure [289] but the reaction with 2-sulfinylaminobenzoyl chloride (126a) under the Kametani's conditions [227,228] was not successful due to the insolubility of 124. Use of lithium bis(trimethylsilyl)amide for deprotonation of 124 allowed successful quinazolinone annelation with 126a in THF at rt for 2 h to furnish 26 in 85% yield (Scheme 29) [285]. Dallavalle et al. developed one-pot, three-step synthesis of 26 from 124 [286]. They prepared 124 by Friedländer condensation of N-allylpyrrolidine-2,3-dione 127 with anthranylaldehyde 114, followed by deprotection of allylic group after palladium-catalyzed isomerization to enamide function (Scheme 29). A one-pot sequence of acylation of 124 with 2-nitrobenzoylchloride (126b) (NaH, THF, 60 °C, 1 h), reduction of the nitro group (Fe, AcOH/EtOH, reflux, 2 h) and subsequent ring-closure led to 26 (38%) [286]. Mw-assisted rapid synthesis of 26 (85% yield) via the cyclocondensation of the amide 124 with isatoic anhydride 126c has been fulfilled by Yadav et al. under solvent-free conditions [287]. Jahng et al. developed facile synthesis of 26 as well as rutaecarpine and tryptanthrin via cyclocondensation of iminochlo-ride derived from lactams with methyl anthranylate 126d. Application of this quinazolinone annelation for 124 furnished 26 in 88% yield [229]. A unique hetero Diels—Alder synthesis of the key intermediate 124 was developed by Stevenson et al. [288]. A Lewis acid catalyzed [4 + 2] cycloaddition reaction between azetin 128 and imine 129 yielded quinoline derivative 130, which underwent base-catalyzed cyclization to give the amide 124 in a high yield (Scheme 29). For synthesis of luotonin A analogues and SAR studies, see the review of Ma et al. [29] and references cited therein.

0 0

Post a comment