872327-46-3Relevant academic research and scientific papers
Iodine-mediated electrophilic cyclization of 2-alkynyl-1-methylene azide aromatics leading to highly substituted isoquinolines and its application to the synthesis of norchelerythrine
Fischer, Dirk,Tomeba, Hisamitsu,Pahadi, Nirmal K.,Patil, Nitin T.,Huo, Zhibao,Yamamoto, Yoshinori
supporting information; scheme or table, p. 15720 - 15725 (2009/03/12)
The reaction of 2-alkynyl-1-methylene azide aromatics 1 with iodine and/or other iodium donors, such as the Barluenga reagent (Py2IBF 4/HBF4) and NIS, gave highly substituted cyclization products, namely, the 1,3-disubstituted 4-iodoisoquinolines 2, in good to high yields. Not only simple 2-alkynyl benzyl azides 1a-j and their substituted analogues 1k-u and 6 but also heteroaromatic analogues, including pyridine 8, pyrroles 10a-c, furane 10d, and thiophenes 10e-g, gave the corresponding isoquinoline derivatives in excellent to allowable yields. Electron-donating and electron-accepting substituents on the aromatic ring were equally tolerated, and either acidic or basic (or even neutral) reaction conditions, depending on the reactivity of the substrate, could be applied to smoothly convert the azide starting materials into the desired isoquinoline products in moderate to good yields. Limits were found only in connection with the substituent at the alkyne terminus, where electron-neutral or electron-donating substituents are clearly favored. The iodine-mediated electrophilic cyclization of 1 most probably proceeds through the iodonium ion intermediate 4 followed by nucleophilic cyclization of the azide and subsequent elimination of N2. This new methodology was successfully applied to the short synthesis of norchelerythrine.
The reaction of o-alkynylarene and heteroarene carboxaldehyde derivatives with iodonium ions and nucleophiles: A versatile and regioselective synthesis of 1H-isochromene, naphthalene, indole, benzofuran, and benzothiophene compounds
Barluenga, Jose,Vazquez-Villa, Henar,Merino, Isabel,Ballesteros, Alfredo,Gonzalez, Jose M.
, p. 5790 - 5805 (2008/03/11)
The reaction of o-alkynyl-benzaldehydes 1 with different alcohols, silylated nucleophiles 5, electronrich arenes 10, and heteroarenes 12 in the presence of the reagent IPy2BF4, at room temperature, gave functionalized 4-iodo-1H-isochromenes 2, 6, 11, and 13 in a regioselective manner. When alkynes 16 and alkenes 19 and 20 were used as nucleophiles, a regioselective benzannulation reaction took place to form 1-iodonaphthalenes 17 and 1-naphthyl ketones 18, respectively. Moreover, the latter process has been adapted to accomplish the synthesis of indole, benzofuran, and benzothiophene derivatives (23, 27, and 28, respectively). The three patterns of reactivity observed for the o-alkynylbenzaldehyde derivatives with IPy2BF 4 stem from a common iodinated isobenzopyrylium ion intermediate, A, that evolves in a different way depending on the nucleophile present in the reac-tion medium. A mechanism is proposed and the different reaction pathways observed as a function of the type of nucleophile are discussed. Furthermore, the reaction of the o-hexynyl-benzaldehyde 1b with styrene was monitored by NMR spectroscopy. Compound III, a resting state for the common intermediate in the absence of acid, has been isolated. Its evolution in acid media has been also tested, thereby providing support to the proposed mechanism.
