Platinum‐Catalyzed Hydrogenative Cyclization of Yne‐Enones, Yne‐Aldehydes, and Yne‐Dienes

Abstract

Pt complexes were used in the presence of phosphane ligands, SnCl2, and H2 for coupling reactions of alkynes with electrophiles under environmentally benign hydrogenation conditions, providing five‐ and six‐membered cycloreduction products in moderate to good yield. Deuterium labeling studies suggested the occurrence of a catalytic cycle including the diploar intermediate derived from hydrometalation of a platinum–hydride complex to the alkyne. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Intramolecularly Stabilised Group 10 Metal Stannyl and Stannylene Complexes: Multi‐pathway Synthesis and Observation of Platinum‐to‐Tin Alkyl Transfer

“…(6)] utilising [NnBu 4 ][BF 4 ] (3 equiv) as an ion-exchange reagent. The same strategy was insufficient for fluorinated derivatives 2 b and 2 d, as no chloride exchange occurred with [NnBu 4 ][BF 4 ] (according to 11 B{ 1 H} and 19 F{ 1 H} NMR spectroscopy).…”

“…The stannylene moieties appear as a broad resonance at 62.4 ppm (2 b) and À159.4 ppm (2 d), respectively in the 119 Sn{ 1 H} NMR spectra. The limited solubility of 2 c prevented its analysis by 11 B, 13 C, and 119 Sn NMR spectroscopy.…”

“…Tin dichloride can be applied as a reagent in the palladiumcatalysed hydrostannylation for the selective formation of monoalkyl tin trichlorides. [1] It is also an important co-catalyst for many Group 10 metal-catalysed reactions, such as hydroformylation, [2][3][4][5][6][7][8] 1,5-cyclooctadiene isomerization, [9] cyclization, [10][11][12][13][14] allylation, [15,16] and alkoxycarbonylation of alkenes. [17][18][19][20][21] Although the exact role of SnCl 2 as a co-catalyst is not completely understood, it is believed that it inserts into the MÀCl bond (M = Group 10 metal), forming trichlorostannyl species [MÀSnCl 3 ] where SnCl 3 À serves as a weakly coordinating anion and/or as a trans-labilising ligand.…”

Reactivity of Silyl-Substituted Iron–Platinum Hydride Complexes toward Unsaturated Molecules: 4. Insertion of Fluorinated Aromatic Alkynes into the Platinum–Hydride Bond. Synthesis and Reactivity of Heterobimetallic Dimetallacylopentenone, Dimetallacyclobutene, μ-Vinylidene, and μ2-σ-Alkenyl Complexes

“…The insertion of small unsaturated molecules into the Pt–H bond of mononuclear Pt­(II) complexes has been studied in detail in connection with their role in hydrogenation, hydrosilylation, hydrocyanation, and polymerization reactions . With terminal alkynes RCCH, square-planar σ-alkenyl complexes of the type L n Pt­(CRCH 2 ) or L n Pt­(CHCHR) are generated . Generally, insertion (also called hydrometalation) occurs through the classical “migratory insertion” mechanism, but in some cases radical pathways have been evidenced .…”

Mechanism and Origins of Regio‐ and Enantioselectivities in RhI‐Catalyzed Hydrogenative Couplings of 1,3‐Diynes and Activated Carbonyl Partners: Intervention of a Cumulene Intermediate

“…In contrast, under hydrogenation conditions, catalytic CC coupling occurs with complete atom economy 1g–k. By using rhodium‐based catalysts, hydrogenation of conjugated alkynes (enyne and diynes) in the presence of activated carbonyl compounds and imines delivers CC coupling products,3, 4 and nonconjugated alkynes engage in reductive cyclization with simple unactivated aldehydes 5. Rhodium‐ catalyzed hydrogenation of acetylene in the presence of aldehydes or imines provides products of ( Z )‐butadienylation 6.…”