Facile Synthesis of Carbazoles via a Tandem Iodocyclization with 1,2-Alkyl Migration and Aromatization

Abstract

A strategy for the synthesis of iodocarbazoles through a tandem iodocyclization with migration and aromatization is presented. This sequential cascade process is concisely conducted at room temperature and in a short time. Moreover, the obtained halides can be further applied to palladium-catalyzed coupling reactions, which act as the important intermediates for building other valuable compounds.

Gold-catalyzed intermolecular reaction of ynamides with 3-indolyl azides via an unexpected 1,2-alkyl migration

“…In addition, the reaction also proceeded smoothly with ynamides bearing different R 2 groups, delivering the desired 3f-3j in generally good to excellent yields ( Table 2, entries 6-10). Finally, various 3indolyl azides with different electronic nature on the indole ring were screened, and the reaction furnished the desired products 3k-3n in mostly excellent yields ( Table 2, entries [11][12][13][14]. This transformation thus makes it an alternative way for the efficient construction of the valuable 3-amino-b-carbolines, known as the lead compounds for anti-tumor agents, that conventionally demand rather tedious synthesis [52][53][54][55][56].…”

“…Rearrangement [1][2][3] and migration [4][5][6] reactions as features in the chemistry field have been the focus of considerable attention in the past decades, as they could build surprising and unexpected structures, which are even difficult to synthesize by conventional methods. Among those, intramolecular cyclization of heteroaromatic compounds with alkynes involving alkyl migrations has received particular attention in recent years because this chemistry offers new ways for the efficient construction of synthetically useful heterocycles [7][8][9][10][11][12][13]. For example, Beller and co-workers [7,8] reported an elegant protocol for the platinum-catalyzed synthesis of pyrroloazepinones in 2009, involving a rearrangement of the amidocarbonyl group from the 2-to the 3-position of the pyrrole ring (Scheme 1a).…”

“…In 2012, Hashmi and co-workers [11] disclosed another elegant example of gold-catalyzed synthesis of azepino [3,4-b]indol-1-ones, where an unprecedented 3,2-shift of an acylamino group was involved (Scheme 1c). Very recently, elegant studies on the synthesis of iodocarbazoles through a tandem iodocyclization with migration and aromatization were demonstrated by Liang and co-workers (Scheme 1d) [12]. Despite these significant achievements, these migration reactions have been limited to intramolecular reactions, which may severely limit the molecular flexibility and its further synthetic applications, and such an intermolecular migration reaction has not been reported.…”

Catalyst‐Driven Scaffold Diversity: Selective Synthesis of Spirocycles, Carbazoles and Quinolines from Indolyl Ynones

“…The Ph 3 PAuNTf 2 -mediated carbazole-forming reaction was similarly broad in scope (conditions B);s ome reactions were less efficient than the analogous spirocycle formations, and ynone 1d did not produce any of the desired product( insteads talling at the formation 3d), but the majority of the carbazole products 5a-j werei solated in very good yields. [13] Finally,t he quinoline-formingr eaction sequencew as also found to be very general (conditions C). For ynones 1a-1e,1g,1k-1l,t he sequential AgOTfs pirocyclisation and AlCl 3 ·6 H 2 Om ediated rearrangements teps could both be performed in iPrOH in one-pot as described, whereas for ynones with more sensitivef unctional groups (1f, 1h, 1i, 1j, 1m), the process benefited from as olvent swap,w ith the spirocyclisation first being performed in CH 2 Cl 2 before concentration and addition of iPrOH prior to the AlCl 3 ·6 H 2 Os tep.…”

Carbazoles from the [4C+2C] Reaction of 2,3‐Allenols with Indoles

“…[13] In addition, Liang et al reporteda ni solated example of 1-indol-3-yl-3-alkynol with ICl affording non-N-H 3-iodocarbzaole. [14] We envisioned to use differently substituted 2,3-allenols as the [4C] unit to reactw ith indoles, [15] which may provide as traightforward route to carbazoles with av ery decent diversity and regioselectiovity by considering the unique C3 reactivity of indoles towards the C1 position of 2,3allenols. Here, we wish to report the realization of such ac oncept with the unprotected indoles [16] (Scheme 1).…”