The stereochemistry of the tetrahydropyranes formed by reacting 4‐methyl‐4‐penten‐2‐ol with acetaldehyde. Evidence for a hemiacetal intermediate
- 1 January 1976
- journal article
- research article
- Published by Wiley in Bulletin des Sociétés Chimiques Belges
- Vol. 85 (3) , 151-159
- https://doi.org/10.1002/bscb.19760850307
Abstract
4‐Methyl‐4‐penten‐2‐ol reacts in acidic medium with acetaldehyde to give a mixture of r‐2, cis‐4‐, cis‐6‐, & r‐2, trans‐4, cis‐6‐trimethyl‐4‐tetrahydropyranol (2) and r‐2, cis‐4‐, cis‐6‐, & r‐2, trans‐4, cis‐6‐trimethyl‐4‐(4′‐methylidene‐2′‐pentoxy)‐tetrahydropyrane (3). The third possible isomer, the trans‐2, 6‐dimethyl derivative, could not be detected. This stereochemical outcome strongly suggests a hemiacetal intermediate. The dehydration products of 2, cis‐2,6‐dimethyl‐4‐methylidene‐tetrahydropyrane (5) trans‐and cis‐2, 4, 6‐trimethyl‐5, 6‐dihydro‐2, pyrane (6 and 7) are reported. A half‐chair form for 6 follows from its 1H‐nmr spectrum.Keywords
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