LiHMDS-Mediated Deprotonative Coupling of Toluenes with Ketones.

We demonstrate that lithium hexamethyldisilazide (LiHMDS) acts as an effective base for deprotonative coupling reactions of toluenes with ketones to afford stilbenes. Various functionalities (halogen, OCF3 , amide, Me, aryl, alkenyl, alkynyl, SMe, and SPh) are allowed on the toluenes. Notably, this system proved successful with low-reactive toluenes bearing a large pKa value compared to that of the conjugate acid of LiHMDS (hexamethyldisilazane, 25.8, THF), as demonstrated by 4-phenyltoluene (38.57, THF) and toluene itself (∼43, DMSO).

Catalytic amide base system generated in situ for 1,3-diene formation from allylbenzenes and carbonyls.

The amide base generated in situ from tetramethylammonium fluoride and N(TMS)3 catalyzes the synthesis of 1,3-diene from an allylbenzene and carbonyl compound. The system is applicable to the transformations of a variety of allylbenzenes with functional groups (halogen, methyl, phenyl, methoxy, dimethylamino, ester, and amide moieties). Acyclic and cyclic diaryl ketones, pivalophenone, pivalaldehyde, and isobutyrophenone are used as coupling partners. The role of transß-methyl stilbenes in product formation is also elucidated.

Deprotonative Coupling of Pyridines with Aldehydes Catalyzed by an HMDS-Amide Base Generated in Situ.

Herein, the deprotonative functionalization of pyridine derivatives with aldehydes under ambient conditions has been demonstrated using an amide base generated in situ from a catalytic amount of CsF and a stoichiometric amount of tris(trimethylsilyl)amine (N(TMS)3). Pyridine substrates bearing two electron-withdrawing substituents (i.e., fluoro, chloro, bromo, and trifluoromethyl moieties) at the 3- and 5-positions efficiently react at the 4-position with various aldehydes including arylaldehydes, pivalaldehyde, and cyclohexanecarboxaldehyde.