A total of 19 alkylated heterocycles (thiophenes, benzothiophenes, pyrroles, furans) were prepared (36-99% yield) from the respective pyridin-2-yl-substituted precursors employing alkylboronic acids as the C-H alkylating reagents in an oxidative (Ag2CO3 and 2,6-dimethyl-1,4-benzoquinone as oxidants) Pd-catalysed coupling reaction.
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.
The C(1)–C(13) fragment of the antimitotic marine macrolide leiodermatolide is prepared in 7 steps (LLS) via hydrogenative and transfer hydrogenative reductive C-C couplings. A hydrogen-mediated reductive coupling of acetylene with a Roche-type aldehyde is used to construct C(7)–C(13). A 2-propanol-mediated reductive coupling of allyl acetate with (E)-2-methylbut-2-enal at low loading of iridium (1 mol %) is used to construct C(1)–C(6), which is converted to an allylsilane using Oestereich’s copper-catalyzed allylic substitution of Si-Zn reagents. The union of the C(1)–C(6) and C(7)–C(13) fragments is achieved via stereoselective Sakurai allylation.
N‐tert‐Butoxycarbonyl azide (BocN3) 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(sp3)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.
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