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,

Dibenzothiophene dioxides, which are readily prepared through oxidation of the parent dibenzothiophenes, undergo nucleophilic aromatic substitution with anilines intermolecularly and then intramolecularly to yield the corresponding carbazoles in a single operation. The "aromatic metamorphosis" of dibenzothiophenes into carbazoles does not require any heavy metals. This strategy is also applicable to the synthesis of indoles. Since electron-deficient thiaarene dioxides exhibit interesting reactivity, which is not observed for that the corresponding electron-rich azaarenes, a combination of a thiaarene-dioxide-specific reaction with the SN Ar-based aromatic metamorphosis allows transition-metal-free construction of difficult-to-prepare carbazoles.

Two new palladium-catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into another consists of 1) 4-chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium-catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate, 3) an intramolecular S(N)2 reaction to form a teraryl sulfonium salt, and 4) palladium-catalyzed intramolecular C-S/C-H coupling through electrophilic palladation. Symmetrical as well as unsymmetrical triphenylenes of interest were synthesized in a tailor-made fashion in satisfactory overall yields.

A reactive ketimine intermediate was demonstrated to be intercepted by a variety of nucleophiles including organometallics and TMSCN.

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.

A straightforward synthetic strategy for generating useful anthracene derivatives was developed involving palladium(II)-catalyzed tandem transformation with carboxylic acids as traceless directing groups. Carboxyl-directed C-H alkenylation, carboxyl-directed secondary C-H activation and rollover, intramolecular C-C bond formation, and decarboxylative aromatization are proposed as the key steps in the tandem reaction pathway. This novel synthetic route utilizes a broad range of substrates and provides a convenient synthetic tool that allows access to acenes.

In general, aromatic cores are stable owing to their resonance energies. Different from facile peripheral modifications of aromatic cores, transforming an aromatic core into a different skeleton is ambitious and has attracted only little attention as a general synthetic method. This personal account shows our journey to inventing transformations of dibenzothiophenes into triphenylenes, carbazoles, and spirocyclic diarylfluorenes and to establishing 'aromatic metamorphosis' as a useful and game-changing strategy in organic synthesis. 1 Introduction 2 Aromatic Metamorphosis 3 From Dibenzothiophenes to Triphenylenes 4 From Dibenzothiophenes to Carbazoles 5 From Dibenzothiophenes to Spirocyclic Tetraarylmethanes 6 Conclusion

cycloadditions between ynamides and oxetanes are described; these reactions involve oxetanes and gold-p-ynamides as nucleophiles and electrophiles, respectively. Excellent cycloaddition regioselectivities are achieved over a reasonable range of ynamide and oxetane substrates. For azetidines, their [4+2] cycloadditions with ynamides are implemented more efficiently with silver hexafluoroantimonate, which is also compatible with various ynamides and azetidines. These two cycloadditions provide facile accesses to six-membered heterocycles such as 6-amino-3,4-dihydro-2H-pyrans and 2-amino-1,4,5,6-tetrahydropyridines.