Insights into the Reaction Behaviour of Stannylated Allylic Substrates

Abstract

Stannylated allylic substrates are versatile building blocks for organic synthesis. Pd0‐catalysed coupling reactions of 2‐stannylated allylic carbonates, acetates and phenoxides with amines, malonates, phenoxides, imides and distannanes provide the corresponding substituted allylic compounds, which are suitable for subsequent modifications including Stille coupling reactions. The reaction mechanisms are dependent on the temperature and the nucleophiles used. Tsuji–Trost allylic substitution takes place with organic nucleophiles at low temperature. When distannane is employed at higher temperature, on the other hand, Pd0‐catalysed bismetallation of allenes formed in situ by elimination of tributyltin methoxide predominates.

Palladium‐Catalyzed Chemoselective Allylic Substitution, Suzuki–Miyaura Cross‐Coupling, and Allene Formation of Bifunctional 2‐B(pin)‐Substituted Allylic Acetate Derivatives

“…Kazmaier and co‐workers established one‐pot allylic amination/Stille couplings of β‐stannylated allylic carbonates to provide allylic amine derivatives (Scheme ) 66. 67 This approach provides disubstituted allylic amines and is complementary to the chemistry shown in Table 3, which generates trisubstituted products. After our initial report,15 Pucheault and co‐workers followed with a tandem palladium‐catalyzed Tsuji–Trost allylic substitution/Suzuki–Miyaura cross‐coupling of γ‐borylated allylic acetates (Scheme B) 42.…”

Syntheses of α-Stannylated and α-Iodinated Enamides via Molybdenum-Catalyzed Hydrostannation

“…But with the ynamides 1 in hand, we investigated the molybdenum-catalyzed hydrostannation (Table ). The reactions were carried out in a CO atmosphere, because in previous investigations we observed that CO is beneficial for the lifetime of the catalyst, and higher yields are obtained especially with “critical” substrates such as 1,2-disubstituted alkynes . To our complete satisfaction, also with the ynamides 1 the hydrostannation proceeded cleanly in a highly regio- and stereoselective fashion giving rise to the ( E )-α-stannylation product 2 as the only product in good to high yield.…”

Catalytic Enantioselective Allyl–Allyl Cross-Coupling with a Borylated Allylboronate

“…To more directly address this issue, we considered that installation of a functional group handle on one of the allyl coupling partners might provide a more versatile product motif with well-differentiated alkenes. Herein, we describe a highly enantioselective allyl–allyl cross-coupling reaction that utilizes bis(boryl) nucleophile 1 (Scheme ), such that 3,3′-reductive elimination (i.e., 2 → 3 ) delivers a borylated 1,5-hexadiene framework 3 . These products may be manipulated in a number of ways and should enhance the utility of allyl–allyl cross-coupling in asymmetric synthesis.…”