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 R-p isomers. Furthermore, strong T-shaped pi pi interaction patterns between aromatic C5H3 and C5H4 cycles for three compounds are observed.