Solid–liquid two‐phase alkylation of tetraethyl methylenebisphosphonate under microwave irradiation

Optimum conditions for the solid–liquid phase alkylation of tetraethyl methylenebisphosphonate are dependent on the nature of the alkyl halide. The benzylation with benzyl bromide takes place efficiently in boiling acetonitrile in the presence of potassium carbonate and a phase transfer catalyst. The ethylation with ethyl iodide was best accomplished under solventless microwave conditions in the presence of cesium carbonate and in the absence of an onium salt. The analogous propylation and butylation were complicated by the formation of mixed esters. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:11–, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20648     

Synthesis of cyclic aminomethylphosphonates and aminomethyl‐arylphosphinic acids by an efficient microwave‐mediated phospha‐mannich approach

Microwave‐assisted condensation of 1,3,‐2‐dioxaphosphinane 2‐oxide ( 1 ), paraformaldehyde and secondary amines including 5‐ and 6‐membered N‐heterocycles at 55°C gave cyclic aminomethylphosphonates ( 2 ), whereas an analogous reaction involving dibenzo[c.e][1,2]oxaphosphinane 2‐oxide ( 3 ) resulted in the corresponding aminomethyl‐2‐(2′‐hydroxybiphenyl)phosphinic acids ( 4 ) as a consequence of a hydrolytic ring opening following the condensation. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:207–210, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20387     

Novel 2-phosphabicyclo[2.2.2]oct-5-ene derivatives and their use in phosphinylations

The [4 + 2] cycloaddition of the double-bond isomers ( A and B ) of dihydrophosphinine oxide 1 afforded novel phosphabicyclo[2.2.2]oct-5-ene derivates ( 2–4 ), formation of which was justified by PM3 semiempirical calculations. The compounds of dimer type ( 2–4 ) were utilized in the UV light-mediated fragmentation-related phosphinylation of nucleophiles, especially in that of alcohols. To explore the role of structural modifications on the fragmentation ability, disulfide 5 , phosphabicyclooctane 7 obtained by the hydrogenation of 2 , and the adduct of dihydrophosphinine oxide 1 with benzoquinone ( 7 ) were also synthesized and tested in fragmentation. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:97–106, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10221     

Unexpected condensation reaction of two units of 1,2‐dihydrophosphinine 1‐oxides in the presence of tetracyanoethylene

In the presence of tetracyanoethylene, the reaction of two molecules of dihydrophosphinine oxide 2B followed an unexpected route to afford diphosphatricyclododecatrienes 4 instead of the corresponding Diels–Alder cycloadducts ( 3 ). Structures of the products ( 4 ) have been elucidated by a joint application of spectroscopy and quantum chemical calculations. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:29–35, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10062     

Aggregation of particulate fillers: factors,determination, properties

The aggregation tendency of 11 different CaCO₃ fillers with widely differing particle sizes was studied in polypropylene (PP) composites. The fillers were characterized by different techniques in powder form and in suspension. Homogenization and sample preparation were carried out by extrusion and injection molding, or in an internal mixer and compression molding, respectively. Thin slices were prepared from the composites and the relative area of aggregates was determined by image analysis. Tensile and fracture properties were studied as a function of filler content. The results proved that the extent of aggregation increases with decreasing particle size and increasing filler content. Surprisingly, extruded and injection molded samples contained more aggregates than those prepared by homogenization in an internal mixer followed by compression molding. Good agreement was found between the powder properties of the fillers and their performance in the composites. Deviations from the general tendency indicate that some factors, which were not accounted for in the study, also influence aggregation and composite properties.