Phosphane and Bis(phosphane) Ligands from Phosphinic Acids

Abstract

The Boyd−Regan methodology allowed for access to various cyclic or benzylic mono‐ and bis(phosphinic acids) 1−6. The reduction of monophosphinic acids to secondary phosphanes 7−9 was achieved with silanes. On the other hand, reduction of the bis(phosphinic acids) with LiAlH4 led to bis(phosphanes) 12−13. Various cyclic phosphanes and bis(phosphanes) were obtained by the alkylation of these secondary phosphanes (as their borane adducts). The Michael addition of the same borane adducts to vinylic phosphonates led to phosphane−phosphonates which could be hydrolysed to new hydrosoluble phosphanes.

P‐Chiral Ferrocenephospholanes: Synthesis, Reactivity, Metal Complex Chemistry and Application in the Asymmetric Hydrogenation of Olefins

“…The solvent was evaporated under reduced pressure and the residue was purified by column chromatography (SiO 2 , hexane/EtOAc/NEt 3 100:5:1). Recrystallisation from hot hexane gave compound 7 e as an orange solid (1.20 g, 74 %) (26), 476 (96), 475 (36), 473 (100), 473 (11), 394 (10), 339 (19), 273 (12), 196 (11), 183 (13), 165 (17), 153 (17), 152 (11); elemental analysis calcd (%) for C 24 H 20 BrFeP: C 60.67,H 4.24;found: C 60.73,H 4.20. (R)-(h 5 -2,4-Cyclopentadien-1-yl)(h 5 -1-bromo-2-dicyclohexylphosphino-5ethenylcyclopenta-2,4-dien-1-yl)iron (7 f): n-Butyllithium (1.6 m in hexane, 5.90 mL, 9.44 mmol) was added to a solution of 2,2,6,6-tetramethylpiperidine (1.60 mL, 9.50 mmol) in THF (5 mL) at 0 8C. After 30 min this was added dropwise to a solution of 6 (1.06 g, 3.64 mmol) in THF (15 mL) at À50 8C.…”

“…[30] When our phospholane-iridium complexes were applied under standard conditions they showed only low activities and selectivities. We then investigated the potential of the complexes in the asymmetric hydrogenation of functionalized olefins (16)(17)(18)(19)(20). Table 1 shows the results of these experiments.…”

“…The known examples can be divided into cyclic phosphanes annulated to a cyclopentadienyl ring [18] or cyclic phosphanes connecting the two cyclopentadienyl rings. [19][20][21][22] Herein we report the first synthesis of bicyclic P-chiral ferrocenephospholanes (shown below) based on an orthometalation strategy with a base-induced stereoconvergent intramolecular hydrophosphination as the key step. We also discuss the metal-complex chemistry of these ligands and first results in the rhodium-and iridium-catalyzed asymmetric hydrogenation of olefins.…”

“…There are only a few reports on the synthesis of cyclic ferrocenyl phosphanes (structures of which are shown here). The known examples can be divided into cyclic phosphanes annulated to a cyclopentadienyl ring18 or cyclic phosphanes connecting the two cyclopentadienyl rings 19–22…”

OC004: The fetal neurology clinic. A multidisciplinary approach for the assessment of the fetus with suspected nervous system pathology

“…The second route to phosphinites consists of the nucleophilic substitution of the chlorophosphane 2 , which is obtained by chlorination of the secondary phosphane 3 . Secondary phosphanes usually result from the reduction of phosphinyl chlorides, phosphinates, or phosphinic acids by metal hydrides or silanes 11. The enantiopure phosphinyl chloride 6 was reduced with lithium aluminum hydride to give the pure secondary phosphane 3 in quantitative yield (Scheme ).…”