Contingency and Serendipity in the Reactions of Fischer Carbene Complexes with Conjugated Triynes

Abstract

The first examples of reactions of Fischer carbene complexes with triynes are reported. The regioselectivity of the reaction of the two different alkyne functions in the symmetrical triyne depends on the nature of the substituent of the triyne. Bis-silyl-substituted triynes react at the central alkyne unit, whereas bis-aryl- and bis-alkyl-substituted triynes react at the end alkyne unit. The reaction of a Fischer carbene complex with a phenyl substituent also reacts with a bis-silyl-substituted triyne at the central alkyne unit but gives a furan product rather than the normal phenol product. It was also demonstrated that all three of the alkyne units in conjugated triynes could react in turn with a Fischer carbene complex to give access to trisquinones.

Molecular Assemblies from Imidazolyl‐Containing Haloalkenes and Haloalkynes: Competition between Halogen and Hydrogen Bonding

“…Our synthetic approach was different (Scheme 1): iodoalkyne 2 was synthesized by allowing alkyne 1 to react with N-iodosuccinimide (NIS) in the presence of 10 mol % AgNO 3 . [52] Elemental analysis of the resulting pale-yellow solid gave unsatisfactory results. Furthermore, energy-dispersive spectroscopy (EDS) measurements showed that large amounts of silver were present in the solid, presumably coordinated to the imidazole ring of 2.…”

Intramolecular palladium-catalyzed alkene carboalkynylation

“…We started our investigations by examining the cyclizationalkynylation of diester 5a with triisopropylsilylethynyl bromide (4a) 9 using the conditions developed previously for oxyalkynylation (Pd2(dba)3 with DPE-Phos as ligand, Table 1). Gratifyingly, the desired carboalkynylation product was obtained in 44% yield (entry 1).…”

“…The solid was taken up in DCM and passed through a cotton wool plug, ether was again added to precipitate out the product. After washing with more ether the crude product was dried in (9) …”

A simple, efficient, regioselective and one-pot preparation of N-hydroxy- and N–O-protected hydroxyindoles via cycloaddition of nitrosoarenes with alkynes. Synthetic scope, applications and novel by-products

“…To expand the substrate scope we studied this indolization procedure with new substrates like 1-bromo-2-phenylacetylene 39 and p-tosylacetylene. Three nitrosoarenes with different electronic properties, 4-nitronitrosobenzene, nitrosobenzene and 4-methoxynitrosobenzene, were selected for reaction with 1-bromo-2-phenylacetylene.…”