Easy on, easy off: The N‐(2‐pyridyl)sulfonyl group controls the direct PdII‐catalyzed alkenylation of indoles, affording the corresponding products in good yields and with complete regiocontrol at C2 (see scheme, DMA=dimethylacetamide). The protocol was also extended to pyrrole derivatives. The final reductive desulfonylation affords the C2‐substituted indoles and pyrroles in good yields.

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The easily installed and removed N-(2-pyridyl)sulfonyl group exerts complete C2 regiocontrol over the Pd(II)-catalysed C-H alkenylation of indoles and pyrroles, affording the corresponding products in good isolated yields (typically > or = 70 %). A remarkable feature of this catalyst system is that it tolerates a wide variety of substituted alkenes, including conjugated electron-deficient alkenes, styrenes and 1,3-dienes, as well as conjugated 1,1- and 1,2-disubstituted olefins. The final reductive desulfonylation affords the C2-substituted, free-NH indoles and pyrroles in good yield. This N-(2-pyridyl)sulfonyl-directing strategy has also been extended to the development of a protocol for the intermolecular, dehydrogenative homocoupling of indoles, providing 2,2'-biindoles. Mechanistic work based upon reactions with isotopically labelled starting materials and competitive kinetic studies of electronically varied substrates suggests a chelation-assisted electrophilic aromatic substitution palladation mechanism.

By using DABCO·(SO(2))(2), DABSO, as a solid bench-stable SO(2)-equivalent, the palladium-catalysed aminosulfonylation of aryl-, alkenyl- and heteroaryl halides has been achieved. N,N-Dialkylhydrazines are employed as the N-nucleophiles and provide N-aminosulfonamides as the products in good to excellent yields. The reactions are operationally simple to perform, requiring only a slight excess of SO(2) (1.2-2.2 equiv.), and tolerate a variety of substituents on the halide coupling partner. Variation of the hydrazine component is also demonstrated. The use of N,N-dibenzylhydrazine as the N-nucleophile delivers N-aminosulfonamide products that can be converted into the corresponding primary sulfonamides using a high-yielding, telescoped, deprotection sequence. The ability to employ hydrazine·SO(2) complexes as both the N-nucleophile and SO(2) source is also illustrated.

Flexible friend: The N‐(2‐pyridyl)sulfonyl group acts as a removable directing group in the PdII‐catalyzed aryl CH ortho alkenylation of N‐alkyl aniline, benzylamine, and phenethylamine derivatives with electron‐poor alkenes. The products were obtained in high yields (70–90 %) and with complete regiocontrol. The mild reductive N‐sulfonyl removal enables the construction of a variety of nitrogen heterocycles. EWG=electron‐withdrawing group.

Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: ABSTRACT:The Cu-catalyzed silylation of terminal and internal alkynes bearing a 2-pyridyl sulfonyl group (SO2Py) at the propargylic position affords a breadth of vinyl silanes in good yields and excellent regio-and stereocontrol under mild conditions. The directing SO2Py group is essential in terms of reaction efficiency and chemoselectivity. Importantly, this group also provides the ability to reverse the regiochemical outcome of the reaction, opening the access to either regioisomer without modification of the starting substrate by virtue of an in situ base-promoted alkyne to allene equilibration which takes place prior to the silylcupration process. Furthermore, removal of the directing SO2Py allows for further elaboration of the silylation products. In particular, a onepot tandem alkyne silylation/allylic substitution sequence, in which both steps are catalyzed by the same Cu species, opens up a new approach for the access to either formal hydrosilylation regioisomer of unsymmetrical aliphatic-substituted internal alkynes from propargyl sulfones.

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Leicht hin, leicht weg: In Gegenwart der N‐(2‐Pyridyl)sulfonylgruppe gelingt die direkte PdII‐katalysierte Alkenylierung von Indolen an C2 in guten Ausbeuten (siehe Schema, DMA=Dimethylacetamid). Das Protokoll wurde auf Pyrrolderivate erweitert. Eine anschließende reduktive Desulfonylierung lieferte die C2‐substituierten Indole und Pyrrole ebenfalls in guten Ausbeuten.