Bernard Denise

Assessment of MTO as a catalyst for the synthesis of acid sensitive epoxides. Use of the biphasic system H2O2/CH2Cl2 with and without bipyridine and influence of the substituents on the double bonds

Methyltrioxorhenium (MTO) catalyzes the selective epoxidation of alkenes in the biphasic medium CH2Cl2/H2O2–H2O. Especially sensitive epoxides, which could not be obtained by the use of other reagents, have been isolated in high yield by the addition of bipyridine to this reaction medium.

Unexpected ring opening of cycloaminocarbene complexes of chromium upon alkyne insertion reactions

Abstract Aminocarbenechromium complexes of the general structure (CO)5CrC(R)N-(CH2)nXCH2 (n = 0, X  CH2; n = 1, X  CH2; n = 1, X  CHCH; n = 2, X  molecules of alkyne and one molecule of CO, and CN bond cleavage, new polycyclic heterocycles. The reactions of the pyrroline-, the tetrahydropyridine-, the pyrrolidine- and the methylaziridine-substituted complexes are mainly considered, and the results of X-ray structural studies of the new products are presented. The mechanism of the rearrangement of a 1,5 dipole is discussed.

Transition-metal catalyzed synthesis of δ-hydroxy-γ-lactones from bis(trimethylsilyl) ketene acetals and allylic acetates via γ-unsaturated carboxylic acids. Comments on the formation of α-cyclopropyl carboxylic acids

Abstract Bis(trimethylsilyl)ketene acetals react with allylic acetates in the presence of Pd(0) complexes to give γ-unsaturated carboxylic acids together with α-cyclopropyl carboxylic acids. The unsaturated acids can be converted catalytically to δ-hydroxy-γ-lactones by the H2O2/MTO system (methyltrioxorhenium) and to butenolides by Pd(II) catalyzed intramolecular cyclization reactions. The structure of two of these lactones has been established by X-ray analysis. The mechanism of the formation of the cyclopropanic acids will be discussed.

Copper(II)-catalyzed aerobic oxidation of indane in the presence of aldehydes: intermediate formation of hydroperoxides

Abstract Indane reacts with oxygen, at room temperature, in the presence of isobutyraldehyde, and a copper(II) derivative (Cu(OH) 2 , CuCl 2 , Cu(TPIP) 2 ) to give a mixture of indan-1-yl hydroperoxide and indanone, together with small amounts of indanol. In the presence of Tempo or diphenylamine, as radical scavengers, no reaction takes place. Thus, no direct formation of indanol, as precursor of indanone, via metal-oxo derivatives is likely to occur. The ratio hydroperoxide/indanone is highly dependent on the nature of the transition metal in TPIP-derived complexes.

Reactivity of N-disubstituted aminocarbene complexes of chromium: nitrogen to carbon migration of the benzyl and allyl groups following alkyne insertions

Abstract Chromium aminocarbene complexes (CO)5CrC(CH3)N(CH2Ph)(CH3) (3), (CO)5CrC(H)N(CH2Ph)(CH3) (5) and (CO)5CrC(H)N(CH2CHCH2)(CH3) (7) react with diphenylacetylene in boiling benzene to give, after insertions of the alkyne and CO and migration of the benzyl or the allyl group from nitrogen to carbon, substituted 2- and 3-pyrrolinones (10–15). The structures of (CO)5-CrC(CH3)N(CH2Ph)CH3 (3Z) (R 0.031 Rw 0.030) and of the chromium tricarbonyl complex of the pyrrolinone 10, (CO)3Cr (C24H23ON) (9) (R 0.034 Rw 0.035) were determined by the X-ray diffraction.

Dinuclear μ-alkylidene complexes of transition metals as models for the transformation of CH2X2 (X=Cl, Br, I) into malonic acid derivatives by double carbonylation reactions

Abstract The carbonylation of the μ-alkylidene complexes Fe 2 (CO) 8 CH 2 ) ( 1 ) and Pd 2 I 2 (PPh 2 CH 2 PPh 2 ) 2 CH 2 ( 2 ) has been studied under a variety of conditions. In the presence of an alcohol ROH, complex 1 gives mainly the acetate CH 3 CO 2 R, the product of monocarbonylation, whereas under the same conditions complex 2 gives the malonate CH 2 (CO 2 R) 2 , the product of dicarbonylation. The mechanisms of both reactions are discussed. From the fraction involving 1 a mononuclear complex resulting from the dimerization of ketene has been isolated, and its structure established by an X-ray diffraction study. Olefins such as ethene and norbornene are able to trap the ketene intermediate. The possible participation of such μ-alkylidene complexes in the direct transformation of CH 2 X 2 (X = Cl, Br, I) into malonic acid derivatives is discussed.

Reaction of aminocarbene complexes of chromium and tungsten 6. Rearrangements of and insertions of alkynes into aziridinylcarbene complexes

Abstract Pentacarbonyl[(2-methylaziridinylxmethyl)carbenelchromium(O) (2a) reacts with LiBu followed by H2O to regenerate the starting carbene complex. Treatment of the same reaction mixture with D2O leads to the perdeuteromethyl carbene complex 2D3. However, addition of CH3I instead of D20 gives pentacarbonyl(N-methyl-2-aza-3-methylcyclopentylidene)chromium(O) (28) by ring opening followed by alkylation at nitrogen. The aziridinylcarbene complexes [(CO)5 M = C( NCH(CH 3 )C H2)R1 (M = Cr1, R1 = Me, 2a, R1 = Ph, 2b, R1 = cyclopropyl, 2c react with diphenylacetylene or phenylpropyne) to give 30a-c, 33 and 34 via double alkyne and single CO insertions. However, complex 2d (M = W, R1 = Me) gave only trace amounts of the expected complex 30d. Treatment of 30a with pyridine led to the metal-free derivative 31. Complex 30b (R1 = Ph) was fully characterized by X-ray diffraction.

Synthesis and reactivity of aziridinocarbene complexes of chromium and tungsten: formation of nitrile and acetiminoester complexes

Abstract 2-Methylaziridine H NCH 2 C HCH 3 reacts with alkyl- and aryl-(alkoxy)carbene complexes of chromium and tungsten to give alkyl- and aryl-aziridinocarbene complexes. The latter undergo a thermal transformation to give olefins and alkyl- or aryl-nitrilechromium pentacarbonyl complexes, e.g. (CO) 5 CrNC- o -tolyl (which has been characterized by X-ray crystallography). 2-Phenylaziridine H NCH 2 C HPh in turn reacts with the carbene complexes to give directly styrene and the acetiminoester complexes (CO) 5 WHNC(CH 3 )OCH 2 CH 3 and (CO) 5 CrHNC(CH 3 )OCH 2 -CH 3 . The latter gives, upon hydrolysis (CO) 5 CrNH 3 . The structures of (CO) 5 WHNC(CH 3 )OCH 2 CH 3 and (CO) 5 CrNH 3 have been determined by X-ray diffraction. The mechanisms of the two reactions are discussed.

Reaction of alkoxycarbene complexes of tungsten with 1,2-dihydroquinoline: single vs. double hydride transfers to the carbene-carbon: synthesis, X-ray structure and reactivity of a quinolinium ylide complex of tungsten pentacarbonyl

Abstract The more stable dihydropyridine, 1,2-dihydroquinoline (2), reacts with carbene complex of tungsten (CO)5W(OEt)Ph (3) to give the expected quinolinium complex 4, fully characterized by an X-ray structure. By contrast, under the same conditions complex 7 (CO)5W(OEt)Me led to the alkyltungstate 15 as the result of a double hydride transfer to the carbene–carbon. Complex 15 could be trapped by the enamine of morpholine and cyclohexanone and gave the addition product 14. The quinoline in 4 is easily exchangeable by excess pyridine, via a dissociative mechanism, and gives the known pyridinium ylide complex 5.

X-Ray crystal structure of (tetraphenylimidodiphosphinato)silver(I): an unexpected tetranuclear complex with two modes of coordination of silver

Potassium tetraphenylimidodiphosphinate reacts with silver nitrate to give, upon recrystallization from ethanol, an unexpected tetranuclear complex [Ag{N(OPPh2)2}]4·2EtOH, the structure of which is established by X-ray crystallography; preliminary results concerning its use as a catalyst for the aerobic co-oxidation of alkenes and aldehydes are described.