Rhodium‐Catalyzed N‐tert‐Butoxycarbonyl (Boc) Amination by Directed CH Bond Activation

Abstract

N-tert-Butoxycarbonyl azide (BocN 3 ) was shown to be an efficient and economic source for the directed introduction of N-Boc protected amino groups into the thiophene and benzene nucleus. Yields for the amination of 2-pyridin-2-ylthiophenes (10 examples) were 52-88%. For the amination of the respective benzenes (10 examples) yields between 54% and 99% were recorded with an improved reactivity observed for substrates that bear an electron-withdrawing group. The reaction was applied to short total syntheses of the indoloquinoline alkaloids quindoline and cryptolepine. The facile removal of the Boc protecting group was the key to the success of the syntheses. The scope of the reaction was extended to a C(sp 3 ) À H bond amination and to the amination of 2-phenyloxazoline. For the amination of 2-pyridin-2-ylbenzene a kinetic deuterium isotope effect of 2.0 was determined.

Iridium-Catalyzed C–H Amination of Weinreb Amides: A Facile Pathway toward Anilines and Quinazolin-2,4-diones

“…When 2-naphthyl Weinreb amide was used, the reaction proceeded well with high regioselectivity and a single isomer 2j was formed in 74% yield. Furan or thiophene substrates had been seldom used in the catalytic C–H amination reactions . Interestingly, both furan and thiophene were found to be suitable for this reaction and gave the amination products 2k – m in moderate yield.…”

A Compilation of Synthetic Strategies to Access the Most Utilized Indoloquinoline Motifs

“…Then, this product was treated with py • HCl under heating conditions to give indoloquinoline 2 in quantitative yield (Scheme 18b). [44] 2-Chloro-3-nitroquinoline 81 was employed as the starting material by reacting with phenylboronic acid via Suzuki crosscoupling, followed by reduction of the nitro group to yield 2phenyl-3-aminoquinoline product 82 in moderate yield. Then, the amino group was subjected to Sandmeyer reaction to give iodoquinoline 83 which was further oxidized using 3-chloroper-oxybenzoic acid in the presence of triflic acid to give benzoquinoloiodolium triflate 84 in excellent yield (96%).…”

Isolation, Synthesis, and Biological Activity of Quindoline, a Valuable­ Indoloquinoline Natural Product and Useful Key Intermediate­

“…66 They reacted 2,3-dibromoquinoline (58) with 2-(pivaloylamino)phenylboronic acid (59) under palladium(0) catalysis to access biaryl derivative 60, which was cyclized in boiling 25% H 2 SO 4 to afford quindoline (1) in 85% yield. On the other hand, the fluorinated biaryl 61 was also employed, by Bach and co-workers in 2016, 67 as an intermediate in the synthesis of quindoline through the intermediacy of 57. With the knowledge that azides are a good nitrogen source in transition-metal catalysis, 68 they demonstrated that Boc-azide (BocN 3 ) is an efficient and economic source for the directed introduction of N-Bocprotected amino groups into arenes by the use of C-H activation chemistry.…”