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Syntheses and Reactions of 2,2‐Disubstituted Cyclopentane‐1,3‐diones, 6. Conversion of 2‐Methylcyclopentane‐1,3‐dione into 5‐Methylcycloheptane‐1,4‐dione via 3‐(1‐Methyl‐2,5‐dioxocyclopentyl)propanal
Author(s) -
Schick Hans,
Roatsch Birgit,
Schwarz Hartmut,
Hauser André,
Schwarz Sigfrid
Publication year - 1992
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199219920176
Subject(s) - chemistry , methylcyclopentane , cyclopentane , yield (engineering) , alkylation , aldol reaction , medicinal chemistry , octane , cycloheptane , decarboxylation , aldehyde , intramolecular force , organic chemistry , dehydrogenation , catalysis , stereochemistry , ring (chemistry) , isomerization , materials science , metallurgy
In contrast to earlier reported unsuccessful experiments the Michael addition of prop‐2‐enal to 2‐methylcyclopentane‐1,3‐dione ( 1 ) affords 3‐(1‐methyl‐2,5‐dioxocyclopentyl)propanal ( 3 ) in 90% yield, if the reaction is carried out in water without a basic catalyst. This aldehyde is converted by an intramolecular aldol reaction to (±)‐ endo ‐2‐ and (±)‐ exo ‐2‐hydroxy‐5‐methylbicyclo[3.2.1]octane‐6,8‐dione ( rac ‐ 4 and rac ‐ 6 ), both affording (±)‐5‐methylcycloheptane‐1,4‐dione ( rac ‐ 8 ) after oxidation to (±)‐5‐methylbicyclo[3.2.1]octane‐2,6,8‐trione ( rac ‐ 2 ), hydrolytic ring‐opening and decarboxylation. This reaction sequence allows the transformation of the 2‐alkylated cyclopentane‐1,3‐dione 1 into the 5‐alkylated cycloheptane‐1,4‐dione rac ‐ 8 in a good overall yield. The pathway of the ringopening process has been determined by an investigation of the reaction intermediates.