A nontransmetalation reaction pathway for anionic four-electron donor-based palladacycle-catalyzed addition reactions of arylborons with aldehydes

Tandem Aldol Condensation/Platinacycle‐Catalyzed Addition Reactions of Aldehydes, Methyl Ketones, and Arylboronic Acids

“…Toluene was chosen as the solvent and K 3 PO 4 as the base for our study because they were identified as the best solvent and base in platinacycle 2 -catalyzed addition reactions of arylboronic acids with aldehydes. 3a As a temperature of 80 °C or higher was needed for platinacycle 2 -catalyzed addition reactions of arylboronic acids with aldehydes to occur efficiently, 3a we reasoned that carrying out the tandem reaction at a temperature of lower than 80 °C might suppress the 1,2-addition reaction of arylboronic acids with aldehydes. We thus began our study at 70 °C.…”

“…Because tandem reactions, in which reaction materials are loaded altogether, are operationally more convenient than sequential reactions, it was of interest to us to realize such reactions in a tandem fashion. Based on our previous study that Type I platinacycle 2 12 (Figure 1) -catalyzed 1,2-addition reaction of aldehydes with arylboronic acids occurred slower than that with Type I palladacycles as catalysts, 3a we surmised that that it might be possible to realized the reaction of aldehydes, methyl ketones and arylboronic acids in a tandem fashion by using platinacycle 2 as the 1,4-addition reaction catalyst. 3a,11c Herein, we report our successful realization of such tandem aldol condensation followed by Type I platinacycle 2 -catalyzed addition reactions.…”

“…Although α,β-unsaturated ketones can be “readily” obtained from the aldol condensation of aldehydes and/or ketones, the use of prepurified α,β-unsaturated ketones apparently posed some limits: they’re less available than aldehydes/ketones and require an extra purification/separation step from widely available aldehydes/ketones. During our study of transition metal-catalyzed addition reactions of arylboronic acids with carbonyl-containing compounds, 3,4 we became interested in combining such transition metal-catalyzed addition reactions with the formation of α,β-unsaturated ketones in a sequential or tandem fashion. 5–7 We reasoned that achieving such sequential/tandem reactions would minimize the effort for the preparation of α,β-unsaturated ketones because prepurification for such ketones is eliminated, and may also expand the α,β-unsaturated ketone substrate scope.…”

Efficient Approach to Carbinol Derivatives through Palladium-Catalyzed Base-Free Addition of Aryltriolborates to Aldehydes

“…In 1998, the pioneering work of Miyaura and co-workers [ 17 ] on the rhodium-catalyzed addition reaction of arylboronic acids to aldehydes provided attractive and valuable routes for the synthesis of diarylmethanols. Since then, many examples have been reported by other research groups [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Our group also developed a transition-metal-catalyzed reaction of arylboronic acids with aldehydes under different reaction conditions, leading to the selective synthesis of diaryl ketones [ 33 , 34 ], diarylmethanols [ 35 , 36 ] and aryl benzoate derivatives [ 37 ].…”

[Ir(COD)Cl]2/tris(2,4-di-t-butylphenyl)phosphite-catalyzed addition reactions of arylboronic acids with aldehydes

“…In this context, we have documented air/moisture-stable anionic four-electron donor-based (Type I) palladacycles/platinacycles, 12 a large family of cyclic organometallic compounds, [Rh(COD)Cl] 2 , Ni(COD) 2 /4-RCOC 6 H 4 Cl and CuCl/bipyridine as catalysts for the addition reactions of arylborons with aldehydes, α,β-unsaturated ketones, α-keto esters and aldimines. 13–15 During our study of [Rh(COD)Cl] 2 -catalyzed addition reaction of arylboronic acids with aldehydes, 15b,c we became interested in employing Ir(I) catalysts, particularly with readily available ligands, for such addition reactions. Herein, we report our study on such addition reactions with Ir(I)/phosphite complexes as catalysts, specifically, [Ir(COD)Cl] 2 /tris(2,4-di- t -butylphenyl)phosphite-catalyzed addition reactions of arylboronic acids with aldehydes.…”