1,2-Bis(arylthio)arene synthesis via aryne intermediates.

Lithium 1,1-diadamantylamide (LDAM) base-promoted insertion of arynes into disulfide S-S bonds is described. After generation of arynes from readily available aryl halides and triflates, reactions with diaryl and diisopropyl disulfides afford the insertion products in moderate to excellent yields. Use of 1-cyclohexenyl triflate gave an excellent yield of 1,2-bis(phenylthio)cyclohexene.

New Hindered Amide Base for Aryne Insertion into Si-P, Si-S, Si-N, and C-C Bonds.

A general method for a new, hindered lithium diadamantylamide (LDAM) base-promoted insertion of arynes into Si-P, Si-S, Si-N, and C-C bonds is described. Arynes are generated from easily available aryl triflates and halides. Subsequent reaction of the aryne with silylated phosphines, sulfides, or amines affords the insertion products. Furthermore, a one-step synthesis of anthracenes from aryl halides and aryl ketones is also demonstrated. Cyano, aryl, alkyl, trifluoromethyl, vinyl, methoxy, chloro, fluoro, and even formyl moieties are compatible with the reaction conditions. The new lithium amide affords higher yields compared with lithium tetramethylpiperidide (LiTMP)-promoted reactions. Furthermore, the bulkiness of LDAM base essentially suppresses aryne reaction with base, allowing use of aryl halides and triflates as the limiting reagents.

Synthesis of 1,2-Bis(trifluoromethylthio)arenes via Aryne Intermediates.

A general method for synthesis of 1,2-bis-trifluoromethylthioarenes has been developed. Arynes generated from silyl aryl triflates or halides react with bis(trifluoromethyl)disulfide to afford 1,2-bis-trifluoromethylthioarenes. Aryl, alkyl, ester, halide, and methoxy functionalities are compatible with reaction conditions. Use of bis(perfluoroaryl)disulfides gave moderate yields of aryne disulfenylation or cyclization to fluorinated dibenzothiophenes.

Silylaryl Halides Can Replace Triflates as Aryne Precursors.

Silylaryl bromides and iodides can be prepared in one step from commercially available starting materials. Arynes can be generated from these compounds under conditions nearly identical to those employed for silylaryl triflates. Three distinct transformations, ortho-arylation of N-tritylanilines, intermolecular addition of arynes to amides, and reaction of ureas with arynes, were shown to be successful for the new aryne precursors. The main advantage of silylaryl halides relative to silyl aryl triflates is their one-step preparation from commercially available starting materials.

Hydrogenous Zintl phase Ba3Si4Hx (x = 1-2): transforming Si4 "butterfly" anions into tetrahedral moieties.

The hydride Ba(3)Si(4)H(x) (x = 1-2) was prepared by sintering the Zintl phase Ba(3)Si(4), which contains Si(4)(6-) butterfly-shaped polyanions, in a hydrogen atmosphere at pressures of 10-20 bar and temperatures of around 300 °C. Initial structural analysis using powder neutron and X-ray diffraction data suggested that Ba(3)Si(4)H(x) adopts the Ba(3)Ge(4)C(2) type [space group I4/mcm (No. 140), a ≈ 8.44 Å, c ≈ 11.95 Å, Z = 8] where Ba atoms form a three-dimensional array of corner-condensed octahedra, which are centered by H atoms. Tetrahedron-shaped Si(4) polyanions complete a perovskite-like arrangement. Thus, hydride formation is accompanied by oxidation of the butterfly polyanion, but the model with the composition Ba(3)Si(4)H is not charge-balanced. First-principles computations revealed an alternative structural scenario for Ba(3)Si(4)H(x), which is based on filling pyramidal Ba5 interstices in Ba(3)Si(4). The limiting composition is x = 2 [space group P4(2)/mmm (No. 136), a ≈ 8.4066 Å, c ≈ 12.9186 Å, Z = 8], and for x > 1, Si atoms also adopt tetrahedron-shaped polyanions. Transmission electron microscopy investigations showed that Ba(3)Si(4)H(x) is heavily disordered in the c direction. Most plausible is to assume that Ba(3)Si(4)H(x) has a variable H content (x = 1-2) and corresponds to a random intergrowth of P- and I-type structure blocks. In either form, Ba(3)Si(4)H(x) is classified as an interstitial hydride. Polyanionic hydrides in which H is covalently attached to Si remain elusive.

General method for functionalized polyaryl synthesis via aryne intermediates.

A method for base-promoted arylation of arenes and heterocycles by aryl halides and aryl triflates is described. Additionally, in situ electrophilic trapping of ArLi intermediates generated in the reaction of benzyne with deprotonated arenes or heterocycles has been developed, providing rapid and easy access to a wide range of highly functionalized polyaryls. Base-promoted arylation methodology complements transition-metal-catalyzed direct arylation and allows access to structures that are not easily accessible via other direct arylation methods. The reactions are highly functional-group tolerant, with alkene, ether, dimethylamino, trifluoromethyl, ester, cyano, halide, hydroxyl, and silyl functionalities compatible with reaction conditions.