Synthesis of Enantiomerically Pure N-tert-Butanesulfinyl Imines (tert-Butanesulfinimines) by the Direct Condensation of tert-Butanesulfinamide with Aldehydes and Ketones

Abstract

Experimental details for the first general methods for the one-step preparation of N-tert-butanesulfinyl imines (tert-butanesulfinimines) (2) from aldehydes and ketones is described. To effect the condensations of tert-butanesulfinamide (1) with aldehydes, the Lewis acidic dehydrating agents MgSO4, CuSO4, or Ti(OEt)4 are employed. Aldehyde condensations mediated by MgSO4 proceed in high yields (84−96%) when an excess of aldehyde is used. In contrast, only a slight excess of aldehyde (1.1 equiv) relative to tert-butanesulfinamide provides sulfinimines in high yields when the more Lewis acidic dehydrating agent CuSO4 is used. The CuSO4-mediated procedure is effective for a wide range of aldehydes, including sterically demanding aldehydes, such as isobutyraldehyde (90%), and electron-rich aldehydes, such as p-anisaldehyde (81%). The still more Lewis acidic Ti(OEt)4 and Ti(O-i-Pr)4 also afford N-tert-butanesulfinyl aldimines from especially unreactive aldehydes, such as pivaldehyde (82%). In addition, Ti(OEt)4 is effective for the condensation of 1 with ketones to afford a wide range of N-tert-butanesulfinyl ketimines in good yields (77−91%). For sulfinyl ketimines derived from methyl or n-alkyl phenyl ketones and methyl or n-alkyl isopropyl ketones, only the E isomer is detected by 1H and 13C NMR in CDCl3. For those cases where the difference in steric demand about the imine is very small, such as for 2-hexanone, high E/Z ratios are still observed (5:1).

Stereoselectivity of the Honda–Reformatsky Reaction in Reactions with Ethyl Bromodifluoroacetate with α-Oxygenated Sulfinylimines

“…31,32 As expected, 33 no epimerization of the α-stereocentre was observed with chiral aldehydes. Imines 3-6 were synthesized as model compounds to enable comparison with the stereoinduction exerted by the chiral auxiliaries without the additional bias of an α-oxygenated substituent.…”

A novel method for the synthesis of N-sulfonyl aldimines using AlCl3 under solvent-free conditions (SFC)

“…However, the low nucleophilicity of the latter generally requires harsh acidic conditions to activate the carbonyl group, conditions that are usually incompatible with the resulting unstable sulfonylimines. 25 In a program intended toward developing a cost-effective and direct method to this group of compounds in our laboratory, we exploit a method for preparation of new sulfonylimines 3a-3m. The reaction of the benzaldehyde with p-toluenesulfonamide was chosen as a model and its behavior was studied under a variety of conditions via TLC and NMR spectroscopy (Table 1).…”

Asymmetric aziridination of N-tert-butanesulfinyl imines with phenyldiazomethane via sulfur ylides

“…22,23 H NMR spectra and CDCl 3 (δ = 77.16) was used as a shift reference for 13 C NMR spectra. Elemental analyses were performed by Columbia Analytical Services, Inc. Tucson, AZ.…”