Atropisomer-selective ligand-coupling reactions of sulfoxides. X-Ray molecular and crystal structures for 2-({2-(4-chlorophenyl)naphtho[1,2-b]thiophen-3-yl}amino)-2-methylpropan-1-ol, 2-(2-hydroxy-1,1-dimethylethyl)-2,3-dihydronaphtho[2,1-d]isothiazol-3-one and (R)-(+)-2-bromo-1-(tert-butylsulfinyl)naphthalene

Abstract

1-(Alkyl- or aryl-sulfinyl)naphthalenes activated by electron-withdrawing substituents at the 2-position undergo substitution reactions on treatment with Grignard reagents. Evidence suggesting that these transformations proceed through ligand-coupling reactions of σ-sulfuranes is presented. The ligand-coupling reaction of homochiral sulfoxides with 1-naphthylmagnesium bromide furnishes atropisomeric 1,1′-binaphthyls in 60–95% ee. Single-crystal X-ray structure determinations have been carried out on 2-({2-(4-chlorophenyl)naphtho[1,2-b]thiophen-3-yl}amino)-2-methylpropan-1-ol 18 and 2-(2-hydroxy-1,1-dimethylethyl)-2,3-dihydronaphtho[2,1-d]isothiazol-3-one 22, compounds formed through intramolecular nucleophilic and electrophilic attack, respectively, on a neighbouring oxazoline group. The absolute configuration of (R)-(+)-1-(tert-butylsulfinyl)naphthalene 27 was determined by a single-crystal X-ray study of the 2-bromo derivative 28.