Catalytic Activation of Pinacolyl Allylboronate with Indium(I): Development of a General Catalytic Allylboration of Ketones

Abstract

Hilfe in der Gruppe: Die neuartige Aktivierung eines Gruppe‐13‐Reagens (Bor) durch einen Gruppe‐13‐Katalysator in niedriger Oxidationsstufe (Indium) wurde für die Entwicklung einer allgemeinen katalytischen Allylborierung von Ketonen genutzt. Dieses effiziente C‐C‐Verknüpfungsverfahren ist mit einer Vielzahl an funktionellen Gruppen kompatibel (siehe Schema; B(pin)=Pinacolylboronat).

Palladium(0) versus Nickel(0) Catalysis in Selective Functional‐Group‐Tolerant sp3–sp3 Carbon–Carbon Bond Formations

“…Based on our earlier work on In I -catalyzed allylations of carbonyl derivatives with allyl boronates, [13] we envisioned the use of in situ formed p-allyl-Pd species as electrophiles in a Tsuji-Trost-type reaction [14] with allyl indium(I) nucleophiles, catalytically generated from allyl boronates through boron-to-indium transmetalation. Thus, we initially combined allyl carbonate 1 a and allyl boronate 3 (pin = pinacol-yl) [13] in the presence of [PdA C H T U N G T R E N N U N G (PPh 3 ) 4 ] (10 mol %) in toluene at room temperature with or without indium(I) iodide (20 mol %; Table 1).…”

“…Thus, we initially combined allyl carbonate 1 a and allyl boronate 3 (pin = pinacol-yl) [13] in the presence of [PdA C H T U N G T R E N N U N G (PPh 3 ) 4 ] (10 mol %) in toluene at room temperature with or without indium(I) iodide (20 mol %; Table 1). Unexpectedly, however, the latter reaction (without indium(I)) proceeded more smoothly and provided almost exclusively the linear 1,5-diene 4 a in quantitative yield (as judged by 1 H NMR spectroscopy) after less than 10 min (ratio 4 a/5 a > 32:1, entry 1).…”

“…General: NMR spectra were recorded on a JEOL ECX-400, JEOL ECA-500 spectrometer, or a JEOL ECA-600 spectrometer, operating at 400, 500, or 600 MHz for 1 H NMR and at 100, 125, or 150 MHz for 13 C NMR spectra. Chemical shifts were reported downfield from tetramethylsilane (TMS).…”

Palladium‐Catalyzed Synthesis and Isolation of Functionalized Allylboronic Acids: Selective, Direct Allylboration of Ketones

“…There are very few attempts at the direct allylation of ketones by functionalized allyl-Bpins or their ester analogues reported in the literature. The reactions that have been successful require extreme conditions (for example, 8000 bar and 3 days), which leads to an unselective process;7 therefore, a selective allylboration requires catalytic conditions 8. Some time ago we reported the application of diboronic acid 1 9 (now commercially available) as a boronate source1e, 10 for the Pd-catalyzed borylation of allylic alcohols ( 3 ) to obtain allylboronic acids ( 4 ; Scheme 1).…”

Low‐Valent Indium as a Catalyst for the Allylation of Ketones and N‐Acylhydrazones

“…[7] The working hypothesis for the use of indium(I) halides as catalysts was based upon previous reports in which indium(I) was shown to act as a Lewis base and form a Lewis acid-base complex with boron derivatives. [8,9] Similar to other Lewis base catalysis, indium(I) could enhance the nucleophilicity of the allylborane towards the ketone.…”