Oxaspiro octanes synthesis

The reaction involving the alkylation of p-hydroxyalkyl selenides to give p-hydroxyalkylselenonium salts which are then cyclized with a base is by far the most general. It allows Ae synthesis of a large variety of epoxides such as tenninal, a,a- and a,p-disubstituted, tri-33-> and tetra-substituted, 3,i88 as oxaspiro[2.0.n]-hexanes, -heptanes and -octanes (Scheme 161, g Scheme 162, d Scheme 164, d Scheme 165, b) - and vinyl oxiranes (Schemes 166 and 181)33 -239 from both p-hydroxy-alkyl methyl33- 3 3 22>.222j36,263 phenyl selenides. ... 

Tetramethyl-l-oxaspiro-(2,5)octane is conventionally obtained in a multi-step synthesis from readily available (-)-(5)- -citronellol or (H-)-(/ )-pulegone (Figure 8) [41], In the presence of acidic catalysts it rearranges to the industrially-desired 2,2,3,6-tetramethylcyclohexane carbaldehyde (17) and many other products. 

Isomerization of 4,4,5,8-Tetramethyl-l-oxa- piro 2.5 octane - 4,4,5,8-Tetra-methyl-l-oxaspiro[2.5]octane (1) is obtained in a multistep synthesis from easily available ( —)-(5)-P-citronellol or (+)-/ -pulegone. It reacts to the industrially-desired 2,2,3,6-tetramethyl-cyclohexane-carbaldehyde (2) (Figure 5) in the presence of acidic catalysts beside many other by-products. 

Chloracetonitrile added dropwise to a vigorously stirred mixture of cyclohexanone, benzyltriethylammonium diloride, and aq. 50%-NaOH, the product isolated after 0.5 hr. at 15-20 l-oxaspiro[5.2]-octane-2-carbonitrile. Y 79%. F. e. s. A. Jonczyk, M. Fedorynski, and M. Makosza, Tetrah. Let. 1972, 2395 quaternary ammonium compds. as reagents and catalysts, review, s. J. Dockx, Synthesis 1973, 441. 

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