Planar Chirality from the Chiral Pool: Diastereoselective Anionic Phospho-Fries Rearrangements at Ferrocene

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.