Diamines, unsymmetrical, asymmetric

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... 

The Barbas group further identified catalyst Id for asymmetric Michael additions using brine as the reaction medium 10 mol% diamine Id/TFA at ambient temperature afforded q n-Michael adducts in high yields and good to excellent stereoselectivities for cyclic ketones. The stereoselectivities decreased when aliphatic aldehydes were used as donors (Scheme 9.13). Moreover, the same authors demonstrated the first example of sym-metrical/unsymmetrical a,a-diallgrlaldehydes as donors in asymmetric Michael reactions to produce adducts featuring an all-carbon quaternary stereocentre. The use of 30 mol% (S )-l-(2-pyrrolidinylmethyl)pyrrolidine la in combination with an equal amount of TFA yielded products with moderate to high levels of diastereo- and enantioselectivity (Scheme 9.14). ... 

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