69145-11-5Relevant academic research and scientific papers
Planar chirality from the chiral pool: Diastereoselective anionic phospho-fries rearrangements at ferrocene
Korb, Marcus,Lang, Heinrich
, p. 6643 - 6659 (2014)
Exclusively, the anionic phospho-Fries rearrangement has successfully been adopted on chiral ferrocenyl phosphates, resulting in diastereomeric enriched 1,2-P,O-phosphonates (up to 95% de), which can further be converted to an enantiomerically pure phosphane. A simple synthetic protocol for the preparation of all starting materials based on several chiral-pool alcohols, chiral (di)chlorophosphates, and the respective ferrocenyl phosphates is reported. Optimized reaction conditions for the anionic phospho-Fries rearrangement allow conversions at ambient temperature and the use of variable lithium amid bases and diamines in hexane, ensure virtually quantitative yields, and avoid side reactions. The (bi)cyclic alkyl substituents result in air- and moisture-stable compounds and furthermore allow the conversion of 1,1′-substituted derivatives to 1,1′,2,2′-functionalized ferrocenes, which is reported for the first time. Simultaneous rearrangements at diferrocenyl phosphates to phosphinates and even 2-hydroxy-1,3-bis(phosphonato) ferrocenes and their workup under ambient conditions can be performed. Single-crystal diffraction analysis allowed the determination of the absolute configuration of the planar chirality of two diastereomerically pure ferrocenes being the Rp isomers. Furthermore, strong T-shaped π-π interaction patterns between aromatic C5H3 and C5H4 cycles for three compounds are observed.
Stereochemistry of the methoxide induced rearrangement of an α-bromophosphonamidate: Cleavage of the P-N and P-C bonds in the azaphosphiridine oxide intermediate
Harger, Martin J. P.,Sreedharan-Menon, Ramesh
, p. 527 - 532 (2007/10/03)
Menthyl P-(bromomethyl)-N-tert-butylphosphonamidate 5 has been prepared from (1R,2S,5R)-(-)-menthol and the SP diastereoisomer has been isolated. This rearranges with methoxide [Me3(PhCH2)N+ MeO- in THF-MeOH] to give only the SP diastereoisomer of menthyl methyl (tert-butylamino)-methylphosphonate 6 and very largely (95%) the SP diastereoisomer of menthyl methyl N-tert-butyl-N-methylphosphoramidate 7. The configurations of these products show that when the (postulated) azaphosphiridine oxide intermediate 16 suffers ring opening by methoxide, the P-N bond is cleaved (to give 6) with inversion of configuration but the P-C bond is cleaved (to give 7) with predominant retention. These contrasting stereochemistries suggest that nucleophilic attack on the P=O group of the azaphosphiridine oxide generates a five-coordinate intermediate (not merely a transition state) that exists long enough to undergo pseudorotation.
