TfOH-Catalyzed One-Pot Domino Reaction for Diastereoselective Synthesis of Polysubstituted Tetrahydrospiro[carbazole-1,3′-indoline]s

Abstract

TfOH-catalyzed one-pot sequential reaction of indoles, acetophenones (cyclic ketones), and various 3-methyleneoxindolines in toluene afforded polysubstituted tetrahydrospiro[carbazole-1,3'-indoline]s in satisfactory yields. H NMR spectra and single-crystal structures indicated that the obtained tetrahydrospiro[carbazole-1,3'-indoline]s existing in an unusual trans-configuration. The reaction mechanism was believed to proceed with domino acid-catalyzed 3-alkenylation of indoles with acetophenones, Diels-Alder reaction of 3-alkyenylindoles with 3-methyleneoxindolines, and an acid-catalyzed diastereoisomerization process.

Selective Synthesis of 3-(9H-Carbazol-2-yl)indolin-2-ones and Spiro[tetrahydrocarbazole-3,3′-oxindoles] via a HOTf Catalyzed Three-Component Reaction

“…However, a little spiro product derived from the normal Diels−Alder reaction can be detected in the reaction of cyclohexanone. 14 The structures of the obtained compounds 5a−5k were established on the spectroscopy. The single-crystal structure of the compound 5g (Figure 2) was also successfully determined by X-ray diffraction.…”

Dual Palladium/Scandium Catalysis toward Rotationally Hindered C3‐Naphthylated Indoles from β‐Alkynyl Ketones and o‐Alkynyl Anilines

“…Next, Sc(OTf) 3 is believed to activate the carbonyl group of the β‐alkynyl ketone 1 , trapped by indole C to the tertiary alcohol anion intermediate E , which undergoes dehydration and releases Sc(OTf) 3 to the 1,5‐enyne intermediate F . [ 47‐48 ] Finally, PdCl 2 activates the carbon‐carbon triple bond of the intermediate F to promote an intramolecular 6‐ endo‐dig cyclization, offering the intermediate H , which converts into the target products 3 through proton transfer (PT) and regenerates the Pd catalyst.…”

Efficient synthesis of polyfunctionalized carbazoles and pyrrolo[3,4-c]carbazoles via domino Diels–Alder reaction

“…Therefore, the Diels-Alder reaction of activated 2-vinylindolines or 3-vinylindolines with diverse dienophiles has become the most attractive strategy for the synthesis of carbazole deriv- atives [28][29][30][31][32][33][34][35][36][37][38][39][40]. In recent years, by using the one-pot domino synthetic strategy of in situ-generated 2-vinyl-or 3-vinylindolines and sequential Diels-Alder reaction with activated dienophiles, we have successfully developed several efficient synthetic protocols for diversely functionalized tetrahydrocarbazoles and the corresponding carbazole derivatives [41][42][43][44][45][46][47]. To further demonstrate the synthetic application of domino Diels-Alder reactions and in continuation of our aim to providing efficient domino reactions for the synthesis of biologically important carbazole derivatives [48][49][50][51][52][53], herein we wish to report the DDQ-mediated dehydrogenative Diels-Alder reaction of 3-(indol-3-yl)maleimides and benzoyl-substituted 3-ethylindoles with readily available chalcones for the convenient synthesis of polyfunctionalized carbazole derivatives.…”