Heteroaryl N-Boc imines

The aza-Henry reaction promoted by catalyst 31 deserves special attention. This bifunctional catalyst, which displays an additional hydrogen bond donor, afforded the best results in terms of yield and selectivity for the addition of nitromethane, nitroethane, or 1-nitropropane to various aryl and heteroaryl N-Boc imines (Scheme 29.13) [37]. Reactions carried out in acetonitrile at -20°C, employing 10mol% catalyst, provided the highest stereoselectivities achieved so far. 

An interesting protocol to concurrently produce adjacent quaternary and tertiary stereogenic centers was described employing the bifunctional thiourea-secondary amine 34, which promotes the addition of methyl 2-nitropropanoate to aryl and heteroaryl N-Boc imines. In this particular case, the secondary amine N-H group present in the catalyst seemed to play an additional role other than merely acting as a Br0nsted base (Scheme 29.17) [41],... 

Scheme 29.33 Thiourea 61 catalyzed addition of heteroaryl P-ketosulfones to N-Boc imines. 29.4...

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