F. Guibe

The allyloxycarbonyl group for alcohol protection: quantitative removal or transformation into allyl protecting group via π-allyl complexes of palladium

Abstract In the presence of Pd catalysts and under mild, essentially nonbasic conditions, the allyloxycarbonyl derivatives of alcohols may be either converted into the corresponding allyl ethers or hydrogenolysed (Bu 3 SnH) back to the starting alcohol.

Use of an allylic anchor group and of its palladium catalyzed hydrostannolytic cleavage in the solid phase synthesis of protected peptide fragments

Abstract The allylic handle ue5f8Oue5f8CH 2 ue5f8CHue5fbCHue5f8CH 2 ue5f8Oue5f8CH 2 ue5f8COue5f8 has been used in the synthesis of protected peptide fragments on aminomethyl polystyrene. The palladium-catalyzed hydrostannolytic cleavage of the peptide fragments from the resin occurs under very mild conditions.

Palladium catalyzed hydrostannation of alkynes and palladium-catalyzed hydrostannolysis of propargyl or propargyloxycarbonyl derivatives of various functional groups

Abstract PdCl 2 (PPh 3 ) catalyses, under very mild conditions, the cis-hydrostannation of acetylenic compounds by tributyltin hydride and the hydrostannolytic cleavage of propargyl carboxylates, phosphates, carbonates and carbamates. The latter reaction should find use in protective group chemistry.

Selective palladium-catalyzed deprotection of the allyl and allyloxycarbonyl groups in phosphate chemistry and in the presence of propargyl and propargyloxycarbonyl groups

Abstract The allyl group is shown to be orthogonal to the most commonly used phosphate protecting groups. In some cases, the allyl and allyloxycarbonyl groups may be selectively cleaved, under palladium-catalysis, in the presence of the propargyl and propargyloxycarbonyl groups.

Rearrangements d'allyloxy-pyridines catalyses par les complexes du platine(o)

Abstract Zerovalent Platinum complexes catalyse the conversion of allyloxy-pyridines into N-allyl pyridones. The results can be rationalized by assuming an intermediate π allylic complex.

New potential access to ethylenic pseudodipeptides through catalytic alkene metathesis

Dialkenenic amide 1 (R1= CH2Ph, R2= H) is readily converted, through ruthenium-catalysed metathetic ring closure, to ethylenic lactam 2, a close precursor of Z-ethylenic pseudodipeptide 3.

N α -Alloc temporary protection in solid-phase peptide synthesis. The use of amine–borane complexes as allyl group scavengers

The use of a combination of amine–borane complexes and soluble palladium catalyst allows the fast deprotection of allyl carbamates under near-to-neutral conditions and without any side-formation of allylamine. Preliminary experiments indicate that palladium catalyst–amine–borane systems seem ideally suited for removal of Nα-Alloc terminal groups during solid phase peptide synthesis according to the N n α-Alloc temporary protection strategy.

Reduction of some polyhalogenato- and polyacetoxy-allylic compunds using tributyltin hydride in the presence or absence of palladium catalyst: II. Reduction of 1,1,1,4-tetrachlorobut-2-ene☆

Abstract The radical tributyltin hydride reduction of 1,1,1,4-tetrachlorobut-2-ene yields a mixture of the expected 1,1,4-trichlorobut-2-ene and 1,1,4-trichlorobut-1-ene resulting from preferential abstraction of a chlorine atom from the trichloromethyl group. The palladium-catalyzed reduction follows an entirely different course, giving 1,1-dichlorobutadiene exclusively and quantitatively. The palladium-catalyzed reaction involves an oxidative addition-β-elimination process leading to dichlorobutadiene and a dichloropalladium(II) species. Tributyltin hydride reduction of palladium(II) to palladium(O) completes the catalytic cycle.

Reduction of some polyhalogenato- and polyacetoxy- alyllic compounds with tributylin hydride in the presence or absence of a palladium catalyst: I. Reduction of dichloro- and diacetoxy-propenes

Abstract Radical-promoted tributylin hydride reduction of 3,3-dichloropropene, ( Z )-1,3- dichloropropene, or ( E )-1,3-dichloropropene yields a mixture of the three possible regio-stereoisomeric monochloropropenes. The palladium-catalyzed reduction yields regiospecifically the two stereoisomeric 1-chloropropenes with a Z/E ratio which remains constant whatever the starting dichloropropene but which is not the thermodynamic ratio. The results are against a radical mechanism and strongly support a polar π-allyl mechanism for the catalytic reactions.

Oxidatively induced radical chemistry of dicarbonyl η5-cyclopentadienyl iron derivatives of carboxylic acids (Fp–acyl complexes)

The 17-electron cationic [Fp–acyl] intermediates generated by cerium ammonium nitrate (CAN) oxidation of Fp–acyl complexes in dry acetonitrile undergo a fast homolytic dissociation leading to alkyl radical species whose subsequent fate is dependent on the structural features and reaction conditions.