2-butenylchromium reagents

The addition of the 2-butenylchromium reagent to achiral aldehydes proceeds with excellent anti selectivity, irrespective of whether (E)- or (Z)-l-bromo-2-butene is used as precursor. 

The addition of the 2-butenylchromium reagents to the a-amino aldehydes give predominantly the iyn isomer 245 independently of the nature of the group bonded to the nitrogen (Table 10-27) [146b]. Ohta has recently examined the addition of allyl chromium reagents to Garner s aldehyde [147]. Poor to moderate diastereoselectivity is observed in these reactions. 

Table 10-27. Reaction of 2-butenylchromium reagents with W-protected a-amino aldehydes.

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