Chemistry of gem-Dihalocyclopropanes. IV. Ring Opening of gem-Dichlorocyclopropyl Ethers

A New Platinum Complex Catalyzed Reaction Involving Nucleophilic Substitution at the Central Carbon Atom of the π-Allyl Ligand

“…This alcohol was acetylated as described for 1 in an overall yield of 90% (6.10 g, 27 mmol) to give a colorless liquid, bp 80°C/0. 73.7, 126.6, 128.2, 128.3, 129.4, 132.5, 133.9, 170 (11), 129 (100), 77 (14). Anal.…”

“…The mixture was extracted with pentane and dried over MgSO 4. Evaporation of the pentane followed by distillation gave trans-2-chloro-2-butenal 14 (5.85 g, 56 mmol). This aldehyde was phenylated and acetylated in the same manner as described for 10 using bromobenzene instead of iodomethane in 99% yield (12.4 g, 55 mmol, overall 46% yield) to give a colorless liquid, bp 95°C/0.1 mmHg.…”

A New Approach to Models of the 4,5‐Dihydroxycyclopentenone Core of the Kodaistatins A–D: Elucidation of the Diol Configuration in Kodaistatin A

“…It therefore looked accessible by an aldol addition . The required aldehyde was ( Z )‐2‐chlorobut‐2‐enal ( 12 ), a known compound . Pertinent enolates should stem from dioxolane‐4‐esters of the generic structure 11 .…”

“…As just explained, we needed to add an 11 ‐derived C ‐nucleophile to ( Z )‐2‐chlorobut‐2‐enal ( 12 ) with the highest possible simple and induced diastereoselectivity; plus, the pair of 11 ‐derived C ‐nucleophiles, which should react with opposite simple diastereoselectivities, must react with the same induced diastereoselectivity. Scheme shows how we accomplished both goals.…”

“…We deprotonated the benzyl esters 17 a (acetonide‐protected) and 17 b (cyclohexylidene‐protected), the corresponding methyl esters 17 c and 17 e , and their analog 17 d (cyclopentylidene‐protected) with LDA (lithium diisopropylamide) at −78 °C in THF . The resulting enolates were combined with ( Z )‐2‐chlorobut‐2‐enal ( 12 ). This delivered the aldols 19 a – e overwhelmingly 5, 4 trans , 4, 1′ syn ‐configured .…”