ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The synthesis of the sequiterpenoid tricyclic hydrocarbon (±)-cleovene (1) by application of the α-alkynone cyclisation is described. The starting bicyclic carboxylic acid 2 was obtained from ethyl 3-methyl-2-oxocyclohexane-1-carboxylate by modified known methods (24%) and converted to the α-alkynone 3 (86%). The thermolysis of 3 in the gas phase at 620° selectively produced the tricyclo[6.3.1.01,5] dodecenone 4 (80%) which was converted to 1 (37%) by conventional procedures. The selectivity of the α-alkynone cyclisation is discussed in terms of the stereoelectronic requirements (coplanarity factor) of the carbene insertion. In order to throw further light on the importance of this factor, the (1-adamantyl) alkynone 16 was synthesised from adamantane-1-carboxylic acid (78%) and subjected to thermolysis at 620°. Since this led to the tetracyclo[6.3.1.1.13,10.03,7]tridecenones 17 and 18 (together 72%), we conclude that the planar carbene insertion transition state, while preferred, is not a stringent requirement.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19840670735
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