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Transannular Ring Expansion in the Acid‐Catalyzed Reaction of the Oxirane Derived from Spirocyclopropane‐Substituted Bicyclo[3.2.1]octene
Author(s) -
Adam Waldemar,
Crämer Elisabeth,
Lucchini Vittorio,
Peters EvaMaria,
Peters Karl,
von Schnering Hans Georg,
Staab Eugen
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.19871201018
Subject(s) - cyclopropane , chemistry , trifluoroacetic acid , bicyclic molecule , medicinal chemistry , stereochemistry , ketone , substituent , ring (chemistry) , organic chemistry
Abstract In the reaction of spirocyclopropane‐, oxo‐, and dioxolane‐substituted bicyclo[3.2.1]octenes 2a, b, 7a, 7b with arenesulfenyl chloride the endo ‐3‐chloro‐ exo ‐4‐arylthio addition products 6a, b, 8a, b , and 10 were formed regio‐ and stereoselectively. The stereochemistry of 10 was established by X‐ray structure determination. In the case of spiro [bicyclo[3.2.1]oct‐3‐ene‐6,1′‐cyclopropane] ( 2a ), reaction with arenesulfenyl chloride gave no transannular ring expansion of the spirocyclopropane substituent with or without skeletal rearrangement. However, with trifluoroacetic acid spiro[cyclopropane‐1,8′‐[3]oxatricyclo[4.2.1.0 2,4 ]nonane] ( 3a ) gave the desired 3,8‐disubstituted isotwistane 12a as main product, besides the possible 1,2‐ trans adducts. The sturcture of the latter was established by an X‐ray structure determination of its 3,8‐diol 12b . As an additional side product spiro[2.5]oct‐6‐ene‐4‐acetaldehyde ( 14 ) was formed. Epoxidation of spiro[bicyclo[3.2.1]octa‐3,6‐diene‐2,1′‐cyclopropane] with equimolar m ‐chloroperbenzoic acid ( m ‐CPBA) led preferentially to spiro[cyclopropane‐1,5′‐[3]oxatricyclo[4.2.1.0 2,4 ]non‐7‐ene] ( 4a ) with traces of the 7′,8′‐monoepoxide. Excess m ‐CPBA gave the bisepoxide spiro[cyclopropane‐1,5′‐[3,8]dioxatetracyclo‐[4.3.1.0 2,4 .0 7,9 ]decane] ( 5a ), which with trifluoroacetic acid afforded the epoxy ketone spiro[cyclopropane‐1,6′‐[3]oxatricyclo[3.3.1.0 2,4 ]nonan]‐8′‐one ( 5b ) as minor product and the regio‐ and stereoselective 1,2‐ trans adduct endo ‐8′‐(trifluoro‐acetoxy)spiro[cyclopropane‐1,6′‐ exo ‐[3]oxatricyclo[3.3.1.0 2,4 ]‐nonan]‐ exo ‐7′‐ol ( 15 ) as major product, the latter being formed regio‐ and stereoselectively. Neither 5b nor 15 led to transannular ring expansion of the spirocyclopropane substituent on treatment with trifluoroacetic acid.