Silyl nitronates intermolecular cycloadditions

I. Intermolecular [3+2]-Addition of Nitronates to Olefins Of all known types of nitronates (see Section 3.2), alkyl- and silyl nitronates as well as cyclic C5-C6 nitronates are involved in [3+ 2]-cycloaddition reactions. Detailed comparative kinetic studies for different types of nitronates have not been reported. However, a few data (162, 336, 337) allow one to deduce some sequences (Chart 3.10). 

Silyl nitronates containing chiral inductors have not been as yet used in intermolecular [3 + 2]-cycloaddition reactions. In this case, the facial discrimination was generally created by introducing chiral nonracemic fragments into dipolarophiles (see review 433). 

In intramolecular [3+ 2]-cycloaddition reactions, silyl nitronates also lead to substantially higher stereoselectivity than intermolecular reactions (see, e.g., Scheme 3.178) (193). 

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