A versatile access to unsymmetrical and symmetrical α-diketones via organotin reagents

Catalytic Synthesis of Potassium Acyltrifluoroborates (KATs) through Chemoselective Cross-Coupling with a Bifunctional Reagent

Potassium acyltrifluoroborates (KATs) are increasingly important functional groups, and general methods for their preparation are of great current interest. We report a bifunctional iminium reagent bearing both a tin nucleophile and a trifluoroborate, which was applied in chemoselective Pd⁰ -catalyzed Migita-Kosugi-Stille cross-coupling reactions owith aryl and vinyl halides. This method gives access to previously inaccessible aromatic and α,β-unsaturated acyltrifluoroborates, including precursors to amino-acid derived KATs.

Palladium-catalyzed acetylation of arenes

A simple method for the preparation of aryl methyl ketones is reported. The transformation involves the Pd-catalyzed coupling of an acyl anion equivalent, acetyltrimethylsilane, with aryl bromides to afford the corresponding acetylated arenes in synthetically useful yields. The methodology is tolerant of heterocycles and provides a new method for arene functionalization.

A convenient route to distannanes, oligostannanes, and polystannanes

The quantitative conversion of the tertiary stannane (n-Bu)3SnH (2) into (n-Bu)6Sn2 (4) was achieved by heating the neat hydride material under low pressure or under closed inert atmosphere conditions. A 31% conversion of Ph3SnH (3) to Ph6Sn2 (5) was also observed under low pressure; however, under closed inert atmosphere conditions afforded Ph4Sn (6) as the major product. A mixed distannane, (n-Bu)3SnSnPh3 (7), can also be prepared in good yield utilizing an equal molar ratio of 2 and 3 and the same reaction conditions used to prepare 4. This solvent-free, catalyst-free route to distannanes was extended to a secondary stannane, (n-Bu)2SnH2 (8), which yielded evidence (NMR) for hydride terminated distannane H(n-Bu)2SnSn(n-Bu)2H (9), the polystannane [(n-Bu)2Sn]n (10), and various cyclic stannanes [(n-Bu)2Sn]n=5,6 (11, 12). Further evidence for 10 was afforded by gel permeation chromatography (GPC) where a broad, moderate molecular weight, but highly dispersed polymer, was obtained (Mw = 1.8 × 104 Da, polydispersity index (PDI) = 6.9) and a characteristic UV–vis absorbance (λmax) of ≈370 nm observed.

Palladium complex catalyzed acylation of allylic esters with acylstannanes: complementary method to the acylation with acylsilanes

Palladium-catalyzed acylation of allylic trifluoroacetates (2) using acylstannanes (1) is reported. The reaction serves as a complementary method to the previously reported acylation with acylsilane (4). In particular, the reaction is profitable in the acylation of unsubstituted allyl trifluoroacetate (2a) and benzoylation of allylic trifluoroacetates to afford synthetically useful beta,gamma-unsaturated ketones (3) in good yields without undesirable isomerizations.

Microwave-assisted Syntheses of 1,2-Diketones

A comparative study of the conversion of a number of α-hydroxyketones into 1,2-diketones by three oxidants under microwave irradiation is reported.