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,

Going for gold: The title reaction has been developed and demonstrates a wide substrate scope with respect to the 1,6-enynes and nitrones (see scheme; DCE = 1,2-dichloroethane, Tf = trifluoromethanesulfonyl). The results for the enantioselective versions are also presented.

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 5endo-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.

Two conformationally restricted threedimensional aminoketone scaffolds have been synthesized in only three steps, using a continuous flow photochemistry approach, which is also amenable to scale-up. In addition, several approaches to further derivatize these scaffolds for the synthesis of low molecular weight compound libraries have been detailed.

Catalyst-dependent metathesis reactions between 3-en-1-ynamides and nitrosoarenes are described. Particularly notable are the unprecedented 1,4-metathesis reactions catalyzed by Ag(I) or Zn(II) to give 2-propynimidamides and benzaldehyde derivatives. With 3-en-1-ynamides bearing a cycloalkenyl group, 1,4-oxoimination products were produced efficiently. We have developed metathesis/alkynation cascades for unsubstituted 2-propynimidamides and benzaldehyde species generated in situ, to manifest 1,4-hydroxyimination reactions of 3-en-1-ynes. Both 1,4-oxoiminations and 1,4-hydroxyiminations increase the molecular complexity of products.

Catalytic 1,4-dioxo functionalizations of 3-en-1-ynes to (Z)- and (E)-2-en-1,4-dicarbonyl compounds are described. This regioselective difunctionalization was achieved in one-pot operation through initial alkyne hydration followed by in situ Selectfluor oxidation. The presence of pyridine alters the reaction chemoselectivity to give 4-hydroxy-2-en-1-carbonyl products instead. A cooperative action of pyridine and Zn(II) assists the hydrolysis of key oxonium intermediate.

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Gold-Catalyzed Oxidative Cyclization of 1,5-Enynes Using External Oxidants. -Gold-catalyzed oxidative cyclization of o-(aminoalkynyl)styrenes (I) and (III) in the presence of methylquinoline N-oxide provides access towards indenecarboxamides (II) and (IV) via oxidation of the alkynyl C-2 carbon. In contrast, terminal alkynes like in o-ethynylstyrenes (VI) and (X) are selectively oxidized at the alkynyl C-1 carbon atom to give, after double cyclization process, cyclopropano-fused indan derivatives (VII) and (XI). This reaction cascade proceeds stereospecifically. -(VASU, D.; HUNG, H.-H.; BHUNIA, S.; GAWADE, S. A.; DAS, A.; LIU*, R.-S.; Angew. Chem., Int. Ed. 50 (2011) 30, 6911-6914, http://dx.doi.org/10.1002/anie.201102581 ; Dep. Chem., Natl. Tsing Hua Univ., Hsinchu 30013, Taiwan; Eng.) -Mischke