Synthesis of Calothrixins and Its Analogs Using FeCl₃-Mediated Domino Reaction Protocol

Abstract

A novel one pot synthesis of calothrixin B and its analogs is achieved involving an FeCl3-mediated domino reaction of enamines in dry DMF at reflux. Alternatively, the enamines upon interaction with CuBr2 in DMF at reflux led to the formation of 1-phenylsulfony-2-(2'-nitroaryl)-4-hydroxycarbazole-3-carbaldehydes in excellent yields.

Simple indole alkaloids and those with a nonrearranged monoterpenoid unit

“…Treating 290 with FeCl 3 in boiling DMF provided 285 through electrocyclization/oxidation/reduction of the nitro group/cyclization cascade (Scheme 72). 113 The cycloaddition reaction of furoindole 279 with 3,4-pyridyne, generated from 3-bromopyridine in situ, produced pyridocarbazole 280, which was then converted to ellipticine (278) (Scheme 73). 114 …”

Unusual Reactivity of Aryl Aldehydes with Triethyl Phosphite and Zinc Bromide: A Facile Preparation of Epoxides, Benzisoxazoles, and α‐Hydroxy Phosphonate Esters

“…The reaction of 4,5-dichloro-2-nitrobenzaldehyde (1h, [24] 0.5 g, 2.27 mmol) with triethyl phosphite (0.75 g, 4.54 mmol) in the presence of ZnBr 2 (0.05 g, 0.22 mmol) at room temperature for 10 min followed by workup using general procedure I afforded trans-epoxide 2h …”

ZnO Nanorod Arrays and Hollow Spheres through a Facile Room‐Temperature Solution Route and Their Enhanced Ethanol Gas‐Sensing Properties

“…As part of our studies of Lewis‐acid‐mediated domino reactions,16 we recently reported a synthesis of calothrixin B and its analogs involving an FeCl 3 ‐mediated domino reaction of enamines 17. Prior to this report on calothrixin B, syntheses of quino[4,3‐ b ]carbazole18 and indolo[2,3‐ a ]carbazole19 using a thermal electrocyclization strategy were also achieved in our lab.…”

“…We started our synthesis of calothrixin B from the known 1‐phenylsulfonyl‐2‐nitrophenylvinylindole 7 17. α‐Bromination of 2‐nitroaryl‐3‐acetylindole 7 using phenyltrimethylammonium tribromide (PTT)20 in dry THF gave bromo compound 8 .…”