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Acid‐Catalyzed Reactions of 1‐Oxadispiro[2.1.2.2]nonane: In Search of Transannular Ring Expansion in Monocyclic Substrates
Author(s) -
Adam Waldemar,
Crämer Elisabeth
Publication year - 1987
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19871201202
Subject(s) - chemistry , hydroxymethyl , yield (engineering) , ring (chemistry) , protonation , medicinal chemistry , nonane , trifluoroacetic acid , heptane , stereochemistry , moiety , organic chemistry , ion , materials science , metallurgy
1‐Oxadispiro[2.1.2.2]nonane ( 1 ), prepared in 62% yield by epoxidation of 5‐methylenespiro[2.4]heptane with m ‐chloroperbenzoic acid, gave on treatment with trifluoroacetic acid in CCl 4 the isomeric hydroxy esters 5‐(hydroxymethyl)‐5‐(trifluoroacetoxy)‐( 2a ) and 5‐hydroxy‐5‐[(trifluoroacetoxy)methyl]spiro[2.4]heptane ( 2b ) as major products. Hydrolysis of 2a, b with KOH in ethanol led to 5‐hydroxy‐5‐(hydroxymethyl)spiro[2.4]heptane ( 3 ) in 61% yield. As minor products were isolated the isomeric unsaturated alcohols 5‐(hydroxymethyl)spiro[2.4]hept‐5‐ene and ‐4‐ene ( 4a, b ), spiro [2.4]heptane‐5‐carboxaldehyde ( 5 ) (which was readily autoxidized to carboxylic acid 6 ), and the isomeric acetals 7‐(spiro[2.4]hept‐5‐yl)‐6,8‐dioxadispiro[2.1.4.2]undecane ( 7a, b ). These products were all rationalized in terms of standard carbenium ion chemistry of the protonated oxirane. No evidence could be provided for transannular ring expansion of the spirocyclopropane moiety to yield bridgehead‐substituted norbornanes.