On the Configurational Stability of α-Lithiated Sulfurated Styrene Oxides: Synthetic and Mechanistic Aspects

Abstract

The configurational stability of some sulfurated styrene oxides has been investigated. Chemical studies have shown that in THF at 157 K α-lithiated ortho-and paraphenylthiostyrene oxides are configurationally unstable and undergo a fast racemization on the time scale of the reaction, whereas α-lithiated meta-phenylthiostyrene oxide retains its stereochemical integrity for at least 60 min. The deprotonation-trapping methodology has also been employed for the preparation of a sulfurated β-aminoalcohol effective for the fight against phytopathogenic fungi.

Solvent and TMEDA Effects on the Configurational Stability of Chiral Lithiated Aryloxiranes

“…[37] Racemic and optically active oxiranes 9-11 and 14 were prepared from racemic or optically active 4-(bromophenyl)oxiranes (12) according to previously reported procedures. [27] The spectroscopic data of epoxides 1, [38] 2, [38] 3, [39] 4, [35] 5, [35] 6, [35] 7, [40] 8, [41] 9, [27] 10, [27] 12, [40] 14 [27] and of amino alcohol 16 [27] have been reported previously. For the spectroscopic data of compound 11 see the Supporting Information.…”

“…This is consistent with the fact that lithiated m-fluorostyrene oxide (for which s m (F) = 0.34) is, indeed, configurationally stable. [11,26] It has been said [27] that when the phenylthio substituent is at the ortho or para position of the phenyl ring, strong conjugative interactions involving the low-lying 3d orbitals of the sulfur might play a key role in providing stabilization of the above oxiranyllithiums, thereby triggering racemization. To prove this, the outcome of the deprotonation/deuteration of optically active p-phenylthiostyrene oxide ((R)-10) was compared with that of p-methylthiostyrene oxide ((R)-11) in which the CH 3 S group has a slightly acidifying effect [28] compared with the PhS group.…”