Synthese von Aryl- und Heteroarylindium(III)-Verbindungen durch direkte Insertion von Indium in Gegenwart von LiCl

Charged tags as probes for analyzing organometallic intermediates and monitoring cross-coupling reactions by electrospray-ionization mass spectrometry

Organic iodides bearing a cationic quaternary ammonium group at a remote position react with zerovalent Pd complexes, Zn, or In leading to a C-I bond insertion. The resulting charge-tagged organometallics can be detected by electrospray-ionization mass spectrometry, which provides detailed information on their stoichiometry, oxidation state, and coordination sphere. The properties of the observed organopalladium and -zinc intermediates largely agree with previous findings, whereas the organoindium species show a surprisingly high tendency to form ate complexes. Magnesium also undergoes insertion into the C-I bond of the charge-tagged organic iodides, but instead of the expected organomagnesium intermediates only the corresponding hydrolysis products could be detected in the diluted solutions. Electrospray-ionization mass spectrometry can also be used to study the reactivity of the charge-tagged species, as was demonstrated for a Pd-catalyzed Negishi cross-coupling reaction. The presented approach permits a straightforward identification of the rate-limiting step and the determination of the corresponding second-order rate constant.

LiCl-mediated preparation of functionalized benzylic indium(III) halides and highly chemoselective palladium-catalyzed cross-coupling in a protic cosolvent

Sensitive functional groups such as COR, CHO, or CH(2)OH can be present in benzylic indium reagents prepared by the direct insertion of indium in the presence of LiCl. These reagents undergo palladium-catalyzed cross-coupling reactions in the presence of a protic cosolvent after activation with iPrMgCl x LiCl (see scheme). Remarkable chemoselectivities are achieved by using various electrophiles containing NH or OH groups.