Regio‐ and Stereochemical Studies on the Nitroso‐Diels–Alder Reaction with 1,2‐Disubstituted Dienes |
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Authors: | Dr Gilles Galvani Dr Robert Lett Prof?Dr Cyrille Kouklovsky |
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Institution: | 1. Institut de Chimie Moléculaire et des Matériaux d'Orsay, Batiment 410, Université de Paris‐Sud, 91405 Orsay (France), Fax: (33)?1‐69‐15‐46‐79;2. CNRS, 91405 Orsay (France) |
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Abstract: | 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. |
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Keywords: | asymmetric synthesis cycloadditions enol phosphate nitroso‐Diels– Alder reaction regioselective |
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