R. van Asselt

Palladium complexes containing rigid bidentate nitrogen ligands as catalysts for carboncarbon bond formation

Abstract Zerovalent Pd(Ar-BIAN)(dimethyl fumarate) and divalent PdCl2(Ar-BIAN) complexes containing the rigid bidentate nitrogen ligand bis(arylimino)acenaphtene (Ar-BIAN; Ar = C6H5,p-MeC6H4,p-MeOC6H4) are efficient catalysts for the cross coupling reaction of various organic halides (including acyl-, allyl-, aryl-, benzyl-, vinyl- and 1,2-dienylhalides) with organomagnesium, -zinc and -tin reagents. Coupling reactions of organic halides with one equivalent of organomagnesium and -zinc reagents, in the presence of 1 mol % of a Pd(Ar-BIAN) catalyst, generally proceed smoothly in THF at 20 °C, giving complete conversion of the starting halide within 1–16 hours. Good isolated yields of carbon-carbon coupled products are obtained and the ratio cross/homo coupling varies between 98/2 and 0/100, depending on the substrates used. Reactions employing organotin reagents proceed best in DMF or HMPA and need longer reaction times and/or higher temperatures, as compared to organomagnesium and -zinc reagents, to go to completion. The selectivity for cross coupling is high (generally >99 %) and high isolated yields of cross coupled products can be obtained. In the presence of carbon monoxide (1–5 bar) ketones can be formed with excellent selectivity and in good yields, as was demonstrated for the carbonylative coupling of benzyl bromide with tetramethyltin or (p-tolyl)trimethyltin. Comparison of some Pd(Ar-BIAN) catalyzed reactions with Pd-phosphine catalyzed reactions reveals that these reactions complement each other, for example, when a Pd(Ar-BIAN) catalyst was employed, the coupling of 2-methylallyl chloride with phenyltributyltin was much faster, whereas the coupling of iodobenzene with vinyltrimethyltin was much slower, as compared to the Pd(PPh3)n catalyzed reactions.

SYNTHESIS, STRUCTURE AND REACTIVITY OF BIS(N-ARYL-IMINOPHOSPHORANYL)METHANES. X-RAY CRYSTAL STRUCTURES OF (4-CH3-C6H4-N˭PPh2)2CH2 AND (4-NO2-C6H4-N˭PPh2)2CH2

Abstract The synthesis of novel bis(N-aryl-imino-phosphoranyl)methanes of the type CH2(PR2˭N-Ar)2 has been accomplished by reaction of methylene-bisphosphines with arylazides. These compounds have been fully characterized by 1H, 31P and 13C NMR, IR spectroscopy, Field Desorption Mass Spectroscopy (˭ FDMS) and elemental analysis. Variable temperature NMR experiments and single crystal X-ray structure determinations of CH2(PPh2˭N-C6H4-CH3-4)2 (la) and CH2(PMe2˭N-C6H4-NO2-4)2 (1f) reveal that bis(N-aryl-imino-phosphorany1)methane occurs as tautomer 1. Crystals of la are orthorhombic, space group Pcab, with a = 26.602(2), b = 20.521(1), c = 11.8859(7) A and V = 6488.5(7) A3 (2 = 8, R = 0.045 and Rw = 0.066). The crystals of lf are monoclinic, space group C/2c, with a = 20.153(4), b = 5.952(1), c = 16.930(5) A, β = 106.24(3)° and V = 1949.6(6) A3 (Z = 4, molecular symmetry C2, Rw = 0.051 and R, = 0.079). Both molecules consist of 2 iminophosphoranyl units bridged by a methylene group. The P˭N bond distances of...

A new synthetic route to thiophthalic anhydride derivatives, monomers to poly(isothianaphthene)

Paulussen, H, LIMBURGS UNIV CTR,INST MAT RES,DIV CHEM,UNIV CAMPUS,B-3590 DIEPENBEEK,BELGIUM.