Dirhodium(II) Carboxylate Catalyzed Formation of 1,2,3‐Trisubstituted Indoles from Styryl Azides

Abstract

Dirhodium(II)-carboxylate complexes were discovered to promote the selective migration of acyl groups in trisubstituted styryl azides to form 1,2,3-trisubstituted indoles. The styryl azides are readily available in three steps from cyclobutanone and 2-iodoaniline.

Bio‐Inspired Fragmentations: Rapid Assembly of Indolones, 2‐Quinolinones, and (−)‐Goniomitine

“…Based on our previous utilization of aza‐pinacol rearrangements for the total syntheses of indoline natural products, we envisioned that if the mechanistically related transformation of 3 to 4 could be realized, such a “down to up” fragmentation followed by the regioselective N‐cyclization to the acylium ion intermediate C might offer an efficient strategy to goniomitine by mimicking the biogenetic pathway at the strategic level, namely fragmentation and cyclization (Scheme ). A mechanistically related process involving cationic intermediates was elegantly achieved by the group of Driver through rhodium‐catalyzed reactions of styryl azides, but the reported substrate scope is not applicable to the total synthesis of goniomitine . Our design using an electron‐deficient exocyclic alkene to trigger the fragmentation simplified the precursor to 3 , which could be rapidly assembled by the single‐step convergent coupling of readily available 2‐alkynyl‐anilines 1 and α‐diazo ketones 2 via carbene‐mediated N−H insertion and subsequent intramolecular Michael addition (Scheme ) .…”

“…Am echanistically related process involving cationic intermediates was elegantly achieved by the group of Driver through rhodium-catalyzed reactions of styryl azides,b ut the reported substrate scope is not applicable to the total synthesis of goniomitine. [6] Our design using an electron-deficient exocyclica lkene to trigger the fragmentation simplified the precursor to 3,w hich could be rapidly assembled by the single-step convergent coupling of readily available 2-alkynyl-anilines 1 and a-diazo ketones 2 via carbene-mediated NÀHi nsertion and subsequent intramolecular Michael addition (Scheme 1). [7] Moreover,t he asymmetric establishment of the all-carbon quaternary center (C20) in goniomitine could be traced back to the well-known chemistry of cyclopentanone.…”

Bio‐Inspired Fragmentations: Rapid Assembly of Indolones, 2‐Quinolinones, and (−)‐Goniomitine

“…Herein, we report an alternative mode of fragmentation, namely "down to up" fragmentation, which enables the asymmetric total synthesis of goniomitine in only 5steps (4 manipulations) from readily available starting materials. [6] Our design using an electron-deficient exocyclica lkene to trigger the fragmentation simplified the precursor to 3,w hich could be rapidly assembled by the single-step convergent coupling of readily available 2-alkynyl-anilines 1 and a-diazo ketones 2 via carbene-mediated NÀHi nsertion and subsequent intramolecular Michael addition (Scheme 1). Am echanistically related process involving cationic intermediates was elegantly achieved by the group of Driver through rhodium-catalyzed reactions of styryl azides,b ut the reported substrate scope is not applicable to the total synthesis of goniomitine.…”

ChemInform Abstract: Copper‐Catalyzed Formation of α‐Alkoxycycloalkenones from N‐Tosylhydrazones.

“…As expected from Table 2, we found an inverse correlation between the reaction yield and the size of Angewandte the hydrazone R 1 group.Whenthe aldehyde-derived 13 c was submitted to the reaction conditions,t he naphthalenol 14 c was produced ( Table 3, entry 3). Next, the composition of the ortho-alkenyl substituent was modified (entries [4][5][6][7][8][9][10][11][12]. While shrinking the ring-size led to an attenuated yield (entry 4), substrates containing medium-sized o-cycloalkenyl rings were smoothly converted into the a-methoxy-2H-naphthalenones 14 e and 14 f (entries 5a nd 6).…”

“…This reaction does tolerate acyclic o-alkenyl groups:the hydrazone 13 j was efficiently converted into the 2H-naphthalenone 14 j albeit with areduced yield (entry 10). Thediastereoselectivity of the reaction was next probed (entries [11][12][13][14]. While exposure of the hydrazone 13 k to the reaction conditions provided a3 :2 mixture of diastereomers,t he chiral, nonracemic o-norbornyl 13 l afforded the 2H-naphthalenone product as as ingle diastereomer.N ext, the effect of moving the one of the bridge attachments from the allylic to the homoallylic position was examined with the b-pinene-derived 13 m (entry 13).…”