Untitled

Abstract

Dedicated to Professor Wolfgang Pfleiderer on the occasion of his 75th birthday Starting from methyl 2,3-O-isopropylidene-a-d-mannofuranoside (5), methyl 6-O-benzyl-2,3-O-isopropylidene-a-d-lyxo-hexofuranosid-5-ulose (12) was prepared in three steps. The addition reaction of dimethyl phosphonate to 12, followed by deoxygenation of 5-OH group, provided the 5-deoxy-5-dimethoxyphosphinyla-d-mannofuranoside derivative 15a and the b-l-gulofuranoside isomer 15b. Reduction of 15a and 15b with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by the action of HCl and then H 2 O 2 , afforded the dmannopyranose (17) and l-gulopyranose analog 21, each having a phosphinyl group in the hemiacetal ring. These were converted to the corresponding 1,2,3,4,6-penta-O-acetyl-5-methoxyphosphinyl derivatives 19 and 23, respectively, structures and conformations ( 4 C 1 or 1 C 4 , resp.) of which were established by 1 H-NMR spectroscopy.

Air-stable fluorescent primary phosphine complexes of molybdenum and tungsten

“…As a minor product trans-[Mo(CO) 4 (4) 2 ] 7 was also observed and isolated by column chromatography in a 11% yield. The complex gave a triplet of complex multiplets in the 31 4 (4) 2 ] cis-9 as the major product (Scheme 2). Coordination of the phosphine again resulted in a shift of the 31 P{ 1 H}NMR signal from δ −121.7 ppm for the free phosphine to δ −76.9 ppm for the complex, which showed an increased 1 J PH coupling from 202.5 Hz for the uncoordinated primary phosphine 4 to 388.9 Hz for cis-9.…”

“…All starting materials were purchased from Aldrich, Acros Organics, Alfa Aesar or Strem and used as received. The primary phosphine 8-((4-phosphino)phenyl)-4,4-dimethyl-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene 4 [14], cis-[Mo(CO) 4 (pip) 2 ] [13a] and cis-[W(CO) 4 (pip) 2 ] [15] were prepared according to literature procedures. Flash chromatography was performed on silica gel from Fluorochem (silica gel, 40-63u, 60A).…”

“…The solvent was evaporated and purified by column chromatography (hexane:chloroform 4:1) which yielded a red solid (0.018 g, 10%). 1 4 (pip) 2 ] (0.057 g, 0.126 mmol) and 4 (0.100 g, 0.247 mmol) were dissolved in anhydrous toluene (5 mL) under nitrogen and the reaction was heated to 75 °C for 20 hours. The solvent was evaporated and the complex was purified by column chromatography on silica gel (petroleum ether/dichloromethane 5:1, R f = 0.2) to yield an orange solid (0.092 g, 67%).…”

“…Crystals of cis-7 were grown by slow diffusion (chloroform/pentane) and its solid state structure is given in Figure 1. Typical phosphorus-molybdenum, phosphorus-carbon and molybdenum-carbon bond lengths and the phosphorus-molybdenum-carbon bond angles are as expected ( Figure 1) and compare well with those determined for the related complexes cis-[Mo(CO) 4 [39]. The carbonyls trans to the phosphine ligands exhibit shorter metal-carbon bond lengths than those trans to another carbonyl, which indicates that the carbonyl ligand has a stronger trans influence than the primary phosphine 4 (the same is also true for the tungsten complex 6).…”

“…Their use has therefore been somewhat limited despite the fact they are versatile starting materials with two reactive P-H bonds. Primary phosphines and their derivatives have found applications in medicinal chemistry [2], polymer science [3], carbohydrate functionalization [4], macrocycle synthesis [5] and catalysis [6]. However we have recently developed a working model based on Density Functional Theory which indicates that contrary to popular belief, many primary phosphines will be air-stable if the molecule contains the appropriate degree of π-conjugation or heteroatoms -a stabilizing feature quite separate from the known phenomenon of steric hindrance [7].…”