From ferrocene to decasubstituted enantiopure ferrocene-1,1′-disulfoxide derivatives

The functionalization of (R,R)-S,S '-di-tert-butylferrocene-1,1 '-disulfoxide by deprotolithiation-electrophilic trapping sequences was studied towards polysubstituted, enantiopure derivatives for which the properties were determined. While the 2,2 '-disubstituted ferrocene derivatives were obtained as expected, subsequent functionalization of the 2,2 '-di(phenylthio) and 2,2 '-bis(trimethylsilyl) derivatives occurred primarily at the 4- or 4,4 '-positions. This unusual regioselectivity was discussed in detail in light of pK(a) values and structural data. The less sterically hindered 2,2 '-difluorinated derivative yielded the expected 1,1 ',2,2 ',3,3 '-hexasubstituted ferrocenes by the deprotometallation-trapping sequence. Further functionalization proved possible, leading to early examples of 1,1 ',2,2 ',3,3 ',4,4 '-octa, nona and even decasubstituted ferrocenes. Some of the newly prepared ferrocene-1,1 '-disulfoxides were tested as ligands for enantioselective catalysis and their electrochemical properties were investigated.

Automated summary

The functionalization of (R,R)-S,S'-di-tert-butylferrocene-1,1'-disulfoxide by deprotolithiation-electrophilic trapping sequences was studied, leading to polysubstituted, enantiopure derivatives with determined properties. The regioselectivity of subsequent functionalization was explained based on pK(a) values and structural data. The deprotometallation-trapping sequence allowed for the synthesis of highly substituted ferrocenes, including octa, nona, and decasubstituted derivatives. The prepared ferrocene-1,1'-disulfoxides were tested as ligands for enantioselective catalysis and their electrochemical properties were investigated.