A series of novel
gold(I) complexes bearing galactopyranoside-based
N
-heterocyclic carbene ligands have been synthesized via
transmetalation of the corresponding Ag(I) complex. Gold(I) complexes
have been characterized by NMR, Fourier transform infrared (FTIR),
and elemental analysis. An exhaustive NMR analysis shows that the
complexes are not stable when hydroxyl groups are deprotected. Catalytic
studies, using the alkyne hydration as a model reaction, indicate
that the synthesized complexes are active and reusable.
The solvent-free indium-promoted reaction of alkanoyl chlorides with sterically and electronically diverse arylstannanes is a simple and direct method for the regioselective synthesis of primary, secondary and tertiary alkyl aryl ketones in good to excellent isolated yields (42-84%) under mild and neutral conditions. The protocol is also adequate for the synthesis of aryl vinyl ketones. Reaction times are drastically reduced (from 3-32h to 10-70min) under ultrasonic irradiation. Evidences for the involvement of a homolytic aromatic ipso-substitution mechanism, in which indium metal acts as radical initiator, are presented. It is possible the transference of two aryl groups from tin, thus improving effective mass yield, working with diarylstannanes as starting substrates.
The exceptional leaving group ability of the trimethylstannyl group in electrophilic aromatic substitutions makes possible the synthesis, in a single step, of bi- and triaroylarenes through the catalyst-free, regioselective reaction of bi- and tristannylarenes with different aroyl halides in o-dichlorobenzene as solvent. Specific di- and triketones are obtained in good to excellent yields (45-83%).
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