Nitrones, synthesis Grignard reagents

Addition of the Grignard reagent, prepared from 3-aryl-2-/.sopropyl-1 -chloropropane (340) to nitrone (339) is a very important step toward the synthesis of compound (342a) which is used in preparing the antihypertensive agent SPP-100B and its epimer (342b) (Scheme 2.143) (197). 

Double addition of Grignard reagents to A-glycosyl nitrones (336), in a domino fashion, affords hydroxylamines. Their usefulness has been shown with the synthesis of pyrroloazepine (418) via a ring closing metathesis key step (Scheme 2.187) (564). 

The same nitrone 241 was employed in a stereoselective alkylation with a Grignard reagent by Petrini et al. <1995JOC5706> for another synthesis of lentiginosine. 

Merino P, Castillo E, Franco S, Merchan FL, Tejero T (1998) Nucleophilic Additions of Grignard Reagents to N-benzyl-2,3-0-isopropylidene-D-glyceraldehyde Nitrone (BIGN). Synthesis of (2S,3R) and (2S,3S)-3-phenylisoserine. Tetrahedon 54 12301... 

A sHghdy earher synthesis of (+)-steviamine (eni-352) by Yu and coworkers began with the diastereoselective (de >95%) addition of Grignard reagent 362 to cycHc nitrone 363, derived from D-ribose, to give the adduct... 

The conjugate addition of Grignard reagents to nitroalkenes like 162 leads to magnesium nitronates of type 163, which can be readily converted into nitroalkanes, hydroxymoyl halides, or carlwxylic acids (Scheme 2-64). The reaction of RMgX with nitroalkenes in the presence of CeCls, followed by treatment with 100% acetic acid, has been developed as efficient synthesis of complex nitroalkanes. ... 

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