Regio- and Stereochemical Studies on the Nitroso-Diels-Alder Reaction with 1,2-Disubstituted Dienes

The regioselectivity of the nitroso‐Diels–Alder reaction between unsymmetrical acyclic dienes and Boc‐nitroso (Boc=tert‐butoxycarbonyl) reagent or the Wightman chiral chloronitroso reagents has been studied. With the Boc‐nitroso reagent, the selectivity is a consequence of steric effects at the C1‐p...

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Bibliographic Details
Published in:Chemistry : a European journal 2013-11, Vol.19 (46), p.15604-15614
Main Authors: Galvani, Gilles, Lett, Robert, Kouklovsky, Cyrille
Format: Article
Language:English
Subjects:
asymmetric synthesis
Asymmetry
Chains
Chemistry
Cycloaddition
cycloadditions
Dienes
Electronics
enol phosphate
Isomers
nitroso-Diels-Alder reaction
regioselective
Selectivity
Steric effects
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Summary:The regioselectivity of the nitroso‐Diels–Alder reaction between unsymmetrical acyclic dienes and Boc‐nitroso (Boc=tert‐butoxycarbonyl) reagent or the Wightman chiral chloronitroso reagents has been studied. With the Boc‐nitroso reagent, the selectivity is a consequence of steric effects at the C1‐position in the diene and electronic effects at the C2‐position in the diene. The combination of an unprotected hydroxyethyl side chain at C1 and an electron‐withdrawing group at C2 allows complete regioselectivity in favour of the proximal isomer. The same isomer was obtained exclusively with the chiral nitroso reagent with high enantioselectivities. A model based on steric effects is proposed. Get selective! A combination of steric and electronic effects allows the design of 1,2‐disubstituted dienes for highly regioselective nitroso‐Diels–Alder reactions with either Boc‐nitroso reagent or a chiral chloronitroso reagent. Enantiomerically enriched functionalized cycloadducts could be obtained by asymmetric and regioselective cycloadditions (see scheme; Boc=tert‐butoxycarbonyl, TBS=tert‐butyldimethylsilyl, Piv=pivaloyl).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201302905