Preparation of Functionalized Diaryl‐ and Diheteroaryllanthanum Reagents by Fast Halogen–Lanthanum Exchange

Abstract

Aryl and heteroaryl halides (X=Br, I) undergo a fast and convenient halogen-lanthanum exchange with nBu LaMe, which leads to functionalized diaryl- and diheteroaryllanthanum derivatives. Subsequent trapping reactions with selected electrophiles, such as ketones, aldehydes, or amides, proceeded smoothly at -50 °C in THF, affording polyfunctionalized alcohols and carbonyl derivatives. Kinetic competition experiments revealed a similar reactivity trend as for Br/Mg exchange, but 10 -times higher rates, making it comparable to Br/Li exchange.

Synthesis of Polyfunctionalized Triaryllanthanum Reagents by Using Ph3La and Related Species as Exchange Reagents

“…[8,11] The formation of as table tetrahedral intermediate at À50 8C hampers the subsequent addition reaction, and only traces of overaddition alcohols are observed. [8,11] The formation of as table tetrahedral intermediate at À50 8C hampers the subsequent addition reaction, and only traces of overaddition alcohols are observed.…”

“…[4,5] Organolanthanides are good candidates for fine-tuning the character of the carbon-metal bond, but convenientm ethods fort heir preparation are still scarce. [8] The mixed species nBu 2 LaMe·5LiCl (1)a llows af ast halogen-lanthanum exchange on aryl and heteroaryl bromides and iodides leading to Ar 2 LaMe species, which undergo selective trapping reactions with ar ange of carbonyl compounds and amides. [7] We have reported as traightforwardm ethod to prepare functionalized diaryl-and diheteroaryl-lanthanum derivatives through an ovel halogen-lanthanum exchange.…”

“…[6] They showu seful properties, such as ah igh reactivity towardsc arbonyl compounds, resultingf rom the high oxophilicity and Lewis acidity of lanthanides(III). [8] This exchange proceeds with ah igher functional group tolerance compared with the well-known halogen-lithium exchange [1a,b,e] and with enhanced reaction rates compared with the halogen-magnesium exchange. [8] The mixed species nBu 2 LaMe·5LiCl (1)a llows af ast halogen-lanthanum exchange on aryl and heteroaryl bromides and iodides leading to Ar 2 LaMe species, which undergo selective trapping reactions with ar ange of carbonyl compounds and amides.…”

Herstellung von polyfunktionellen Biarylderivaten durch Cyclolanthanierung von 2‐Bromobiarylen und heterocyclischen Analoga unter Verwendung von nBu2LaCl⋅4 LiCl

“…[2] Die niedrige Elektronegativitätv on Lanthan (1.1) [3] weist, verglichen mit der von Lithium (0.98), auf eine ionische und somit hochreaktive Kohlenstoff-Lanthanbindung hin. Die entstandenen Lanthanheterocyclen sind Schlüsselintermediate fürdie einfa-cheH erstellung von funktionalisierten 2,2'-Diiodobiarylen, Silafluorenen, Fluoren-9-onen, Phenanthrenen und deren verwandten heterocyclischen Analoga.…”

“…[2] Die niedrige Elektronegativitätv on Lanthan (1.1) [3] weist, verglichen mit der von Lithium (0.98), auf eine ionische und somit hochreaktive Kohlenstoff-Lanthanbindung hin. [1] Funktionalisierte Aryl-und Heteroaryllanthanreagenzien, die bereits durch Iod-oder Brom/Lanthanaustauschreaktionen hergestellt werden kçnnen, sind von besonderem Interesse.…”