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

Abstract

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 phosphoFries 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 π−π interaction patterns between aromatic C 5 H 3 and C 5 H 4 cycles for three compounds are observed.

(Planar‐Chiral) Ferrocenylmethanols: From Anionic Homo Phospho‐Fries Rearrangements to α‐Ferrocenyl Carbenium Ions

“…Comparison between 5‐ (type A and B molecules) and six‐membered (type C and D molecules) 1,2‐substituted phosphine Pd complexes and the resulting ee of formed biaryls within Suzuki–Miyaura C , C cross‐coupling reactions. (a) The vinyl group is η 2 ‐coordinated to Pd, which in turn is rotated by 52° out of coplanarity …”

Cobalt‐Catalyzed ortho‐Methylation of Ferrocenes Bearing ortho‐Directing Groups by Catalytic Directed C–H Bond Activation

“…[24] Lithiation and 1,1′-dilithiation are well established, [25] and an ortho-lithiation in the presence of an ODG is also possible. [30,31] We recently reported that the double anionic thia-Fries rearrangement at either one of the cyclopentadienyl ligands takes place in high yield under mild reaction conditions with an unprecedented interannular stereoinduction leading to the exclusive formation of the meso product. [30,31] We recently reported that the double anionic thia-Fries rearrangement at either one of the cyclopentadienyl ligands takes place in high yield under mild reaction conditions with an unprecedented interannular stereoinduction leading to the exclusive formation of the meso product.…”

Multi‐Ferrocenyl Aryl Ethers – Applying Nucleophilic Aromatic Substitution Reactions to Aryl Fluorides

“…The formation of multiple substituted aryl ethers, however, was not observed. The absolute configuration of the planar chirality of the main isomer is assigned to ( R p ) …”

“…), 1,3‐dimethyl‐2‐imidazolidinone, lithium tetramethylpiperidide (LiTMP), hexafluorobenzene ( 2d ), pentafluorobenzene ( 2c ), 1,2,4,5‐tetrafluorobenzene ( 2b ), and 1,3,5‐trifluorobenzene ( 2a ) were purchased from commercial suppliers and were used without further purification. Ferrocenol ( 1 ),, , bis(1 R )‐α‐fenchyl ferrocenyl phosphate ( 7 ), and [N n Bu 4 ][B(C 6 F 5 ) 4 ] were synthesized according to reported procedures.…”

“…Within these studies it could be shown that the use of ortho ‐vinyl,, and ortho ‐ether‐substituted, ferrocenylphosphanes increase the catalytic activity towards the synthesis of biaryls with sterically demanding substituents in the ortho position, due to a stabilization by a hemilabile binding of the ortho substituents . Use of the enantiomerically pure R p ‐isomer of the o ‐methoxyferrocenyl phosphine resulted in the formation of a racemic mixture of triple‐ ortho ‐substituted biaryls . The lack of chiral information was ascribed to the sterically undemanding ortho ‐methoxy group.…”