Nitro Ketones in Organic Synthesis: A New, Short Synthesis of Racemictrans-2-methyl-1,7-dioxaspiro[5.5]undecane,trans, trans- andtrans,cis-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane by Henry reaction
✍ Scribed by Ballini, Roberto ;Bosica, Giovanna ;Schaafstra, Robert
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- English
- Weight
- 235 KB
- Volume
- 1994
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
The synthesis of spiroketals from nitro ketones is described. Racemic trans‐2‐Methyl‐1,7‐dioxaspiro[5.5]undecane (1a), and 2,8‐dimethyl‐1,7‐dioxaspiro[5.5]undecane (1b) are synthesized as a mixture of trans, trans and trans, cis isomers in a ratio of 6.5:3.5 (separable by flash chromatography) by nitroaldol reaction (Henry reaction) of 6‐nitro‐2‐hexanone (2) with THP‐protected hydroxy aldehydes 3 on Amberlyst A21. Subsequent dehydration of the obtained nitro alkanols 4 with Ac~2~O/DMAP affords the nitro alkenes 5 which can be directly converted into 1 by sodium tetrahydridoborate reduction, and refluxing of the reaction mixture after acidification with 2 N HCl.