We report two viable routes for the 1,2-difunctionalization of aminoalkynes using only oxidants. In the presence of a gold catalyst, nitrones enable the oxoamination of aminoalkynes 1 to form 2-aminoamides 2. With a suitable gold catalyst, nitrosobenzenes implement an alkyne/nitroso metathesis of the same substrates to give 2-oxoiminylamides 3. These two novel oxidations also provide 1,2-aminoalcohols with opposite regioselectivity via NaBH(4) reduction in situ.

Pd-catalyzed oxidative cyclizations of 1,6-enynes have found useful applications in organic synthesis, [1] but such reactions with Au and Pt catalysis remain largely unexplored.[2] Goldcatalyzed cycloisomerizations of 1,5-and 1,6-enynes provide uncommon and useful carbocyclic frameworks. [3] In the presence of organic oxidants, most enynes fail to produce oxidative cyclization products because oxidations of hypothetical gold-carbenoid intermediates are difficult. [4,5] Herein, we report two new oxidative cyclizations of 1,5-enynes via 5-endo-dig and 5-exo-dig cyclizations, respectively; both reactions are implemented with Au I and 8-methylquinoline Noxide. The success of such reactions relies on the prior oxidations of enyne [6] form a-carbonyl carbenoids A and B, followed by their intramolecular cyclizations (Scheme 1). Terminal alkynes favor the oxidation at the C2 alkynyl carbon atom and aminoalkynes prefer the C1 carbon atom. Table 1 shows the oxidative cyclization of 2-aminoalkynylstyrene 1 a [7] over commonly used Au I and Pt II catalysts (5 mol %). We employed 8-methylquinoline N-oxide, which exhibited greater catalytic activity than diphenylsulfoxide and other pyridine-based oxides. [8][9][10] Treatment of a solution of 1,5-enyne species 1 a ( We prepared various 1,5-enynes 1 b-l (Table 2) bearing an aminoalkynyl substituent to assess the generality of this oxidative cyclization. Entries 1-5 in Table 2 show the applicability of this catalysis to enynes 1 b-1 f bearing varied electron-withdrawing amino groups including R 2 = Ms and Ts (Ms = methansulfonyl, Ts = toluene-4-sulfonyl), R 3 = Me, nBu, and phenyl to produce 3-carbonyl-1H-indene products 2 b-2 f in good yields (78-92 %). Similar to its analogue 1 a, propan-4-sultam species 1 g was compatible with this catalysis,

No abstract

We report a new redox/cycloaddition cascade on readily available 1-alkynyl-2-nitrobenzenes that produces complex azacyclic compounds stereoselectively. The core structures of the resulting products are constructed through a formal [2 + 2 + 1] cycloaddition among α-carbonyl carbenoids, nitroso species, and external alkenes.

Scheme 3. Deuterium-labeling experiments.Scheme 4. The reaction using diazocarbonyl.Scheme 5. The nature of CÀH insertion.Scheme 6. A plausible reaction mechanism.