Nickel‐Catalyzed Kumada Reaction of Tosylalkanes with Grignard Reagents to Produce Alkenes and Modified Arylketones

Abstract

Neuer Zugang zu Alkenen: Die Kumada‐Kreuzkupplung von Grignard‐Reagentien mit Tosylalkanen bietet einen neuen, selektiven Zugang zu Alkenen ausgehend von Alkyl‐Elektrophilen (siehe Schema).

Modular Synthesis of Triarylmethanes through Palladium‐Catalyzed Sequential Arylation of Methyl Phenyl Sulfone

“…Under these conditions, the desired product was obtained in 49 % yield (entry 7). Whereas the use of K 3 PO 4 as a mild base showed similar reactivity (entry 8), replacement of SIPr with other NHC ligands, such as IMes, ICy, and IAd, resulted in lower reactivity (entries [9][10][11].…”

“…3-Thienylmethyl phenyl sulfone (2 h) was also reactive, but the products were formed in lower yields (entries 11 and 12). Whereas the use of K 3 PO 4 as a mild base showed similar reactivity (entry 8), replacement of SIPr with other NHC ligands, such as IMes, ICy, and IAd, resulted in lower reactivity (entries [9][10][11]. [19] Arylboron compounds, which are air-stable, shelf-stable, functional-group-compatible, and commercially available compounds, were our first choice as a nucleophile.…”

“…Commercially available Pd NHC complexes, such as PEPPSI-IPr, [20] showed similar reactivity (entry 15). Notably, heteroaryl moieties, such as 3-thienyl, 3-furyl, and 3-pyridyl substituents, could also be installed in good to moderate yields (entries [10][11][12]. [21] With optimized conditions in hand, the variation of the aryl boronic acid in the arylation of 4 aa was assessed ( Table 5).…”

“…The reaction with bulky ortho-tolylboronic acid (5 l) was improved by the use of PEPPSI-IPr as the catalyst (entry 9). Notably, heteroaryl moieties, such as 3-thienyl, 3-furyl, and 3-pyridyl substituents, could also be installed in good to moderate yields (entries [10][11][12].…”

“…To accomplish the modular synthesis of triarylmethanes with sufficient generality, we focused on the unique properties of the sulfonyl group: Its electron-withdrawing character dramatically increases the acidity of the protons that are attached to the sp 3 -hybridized carbon atom in the a-position of the SO 2 group, [10] and this functional group simultaneously has the potential to behave as a leaving group for organic reactions. [11] Inspired by recent progress in Pd-catalyzed arylation of acidic C(sp 3 )ÀH bonds [8e-i, 12] and aryl substitution of alkyl electrophiles, [7a-b] we envisioned that these reactions could be used to accomplish the direct installation of three aryl groups on the a-carbon atom of the sulfonyl group, which results in a modular straightforward synthesis of triarylmethanes from readily available building blocks.…”