Two Practical and Efficient Approaches to Fluorinated and Nonfluorinated Chiral beta-Imino Sulfoxides.
Reaction of fluorinated and nonfluorinated N-substituted imidoyl chlorides 1 with lithium derivatives of enantiopure methyl p-tolyl sulfoxide 2a (or racemic methyl phenyl sulfoxide 2b) gave a wide variety of chiral N-substituted beta-imino sulfoxides 4 in good to excellent yields. The title compounds (R)-4 were also prepared by aza-Wittig reaction of gamma-fluoro-beta-keto sulfoxides (R)-5 and N-aryl iminophosphoranes 6. The imino-enamino equilibrium was studied, showing, in all instances, the imino form as the predominant tautomer independent of the nature of the N-substituent. The configuration of the C=N double bond was found to be Z for both N-alkyl and N-aryl derivatives on the basis of (1)H NMR NOE difference experiments performed over several compounds. Ab initio calculations (HF/6-31G) carried out on several representative examples of 1 and 4 are, in general, consistent with the experimental results.
Fustero
Santos
S
C.N.R.-Centro di Studio per le Sostanze Organiche Naturali, Dipartimento di Chimica del Politecnico, via Mancinelli 7, I-20131 Milano, Italy.
Navarro
Antonio
A
Pina
Belén
B
Asensio
Amparo
A
Bravo
Pierfrancesco
P
Crucianelli
Marcello
M
Volonterio
Alessandro
A
Zanda
Matteo
M