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Nitro Ketones in Organic Synthesis: A New, Short Synthesis of Racemic trans ‐2‐methyl‐1,7‐dioxaspiro[5.5]undecane, trans, trans‐ and trans , cis ‐2,8‐dimethyl‐1,7‐dioxaspiro[5.5]undecane by Henry reaction
Author(s) -
Ballini Roberto,
Bosica Giovanna,
Schaafstra Robert
Publication year - 1994
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.199419941215
Subject(s) - undecane , chemistry , nitro , cis–trans isomerism , organic chemistry , medicinal chemistry , alkyl
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.