N-tert-Butanesulfinyl imines

Table 1.2 Diastereoselective addition to N tert butanesulfinyl imines derived from aldehydes.

Propose a mechanism for the following formation of the aza Morita Baylis Hillman reaction product that is obtained from an a hydroxypropargylsilanc (1) and the N tert butanesulfinyl imine. Provide the structure of intermediate A obtained upon slow addition of n BuLi to ( ) 1. 

For diastereoselective addition reactions of trialkoxysilylalkynes to N tert butanesulfinyl imines, see Lettan, R.B. 

In addition to alkenes, imines are tremendously popular aziridine precursors via an aza-Darzens approach. For example, a stereoselective synthesis of C-sulfonylated aziridines was reported via an aza-Darzens approach employing bromomethyl phenyl sulfbne, NaHMDS, and a series of N-tert-butanesulfinyl imines (14MI969). Likewise as shown below, chiral tert-butane- and mesitylsulfinimines were subjected to an aza-Darzens reaction with substituted 2-bromoesters to provide a host of aziridines in good yield with excellent stereocontrol (14OL6920). In turn, these aziridines could be subsequently converted to chiral A/-H aziridines in a total of three steps starting with a wide range of commercially available aldehydes. 

The asymmetric synthesis of unsymmetrical vicinal diamines by samarium diiodide induced reductive coupling of nitrones derived from aUphatic aldehydes with optically pure N-tert-butanesulfinyl aromatic imines has been recently reported [41]. For example, the reaction between nitrone 55 and... 

Ellman and co-workers in 1999 reported on a one-pot method for the asymmetric synthesis of previously protected a-substituted amines by the Ti(OEt)4-mediated NaBELj reduction of A -fcrf-butanesulfinyl ketimines. " The corresponding ketones and N-tert-hatane sulfinamide generated the imines in situ. A rigorous optimization revealed NaBH4 as the best reductant in this case, and... 

Ti(OEt)4 was used for several purposes like as a water scavenger, as a catalyst for imine condensation, and as a Lewis acid to provide an enhanced reaction rate and diastereomeric ratio. The reaction procedures included condensation of the ketones with N-tert-hutane sulfinamide by heating in tetrahydrofuran in the presence of 2 equivalents of Ti(OEt)4. After formation of the corresponding imines, the reaction mixture was cooled to —48°C and added to a solution of NaBH4 in THE at the same temperature. The corresponding a-branched amines were isolated with a high diastereomeric ratio from iV-/cr/-butanesulfinyl imines (Scheme 39.37). 

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