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A rationale of diastereofacial selection in the alkylation of endocyclic enolates with chirality at the β-position

✍ Scribed by Kiyoshi Tomioka; Kōsuke Yasuda; Hisashi Kawasaki; Kenji Koga

Book ID
104218846
Publisher
Elsevier Science
Year
1986
Tongue
French
Weight
254 KB
Volume
27
Category
Article
ISSN
0040-4039

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✦ Synopsis

Ratios of the diastereomers 4 and 5 in the alkylation of the endocyclic enolates 3 with chirality at the B-position were highly dependent on the steric bulkiness of R1 and R2. It was clarified that, when the allylic strain considerations are acknowledged in 3, the diastereofacial selection is successfully rationalized by evaluating two competitive 1,2asymmetric inductions in the conformation 15.

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Diastereofacial selectivity in ketene [2+2] cycloaddition to endocyclic enecarbamates bearing a chiral auxiliary. Synthesis of the (−)-Geissman-Waiss lactone
✍ Paulo Cesar M.L. Miranda; Carlos Roque D. Correia 📂 Article 📅 1999 🏛 Elsevier Science 🌐 French ⚖ 201 KB

The diastereofacial selectivity of enecarbamates bearing a chiral auxiliary was evaluated for the [2+2]cycloaddition with dichloroketenes. Diastereofacial selectivity ranged from zero (bornyl and menthyl) to 60% (Greene's auxiliary and 8-phenylmenthyl). Chromatography separation of the diastereomeri