Cycloheptane-1,2-diols

Reduction, Tropolones are fairly resistant to reducing agents. Catalytic hydrogenation in the presence of Raney nickel or Adams catalyst provides a variety of products including cycloheptanone, cycloheptanol and cycloheptane-1,2-diol derivatives. 

X-ray analysis of the 1,6-diol derivative (15) of the bicydo[4.4.1 ]-undecane ring system revealed the often calculated (9a,81) but rarely observed twist-chair cycloheptane ring. MM calculations confirmed that the observed conformation of 15 is the global minimum conformation (119). 

Incubation of the (1R,2R) diol 25 over a shorter time period of 4 days gave a mixture of the meso cis diol 26 (26%) and the trans diol 25 RR/SS 76 26) showing conversion over to the (1S,2S) diol. As with the previous examples, no conversion was observed when using the S,S diol 25 as a substrate. Although no intermediate a-hydroxyketone was observed for this substrate we proposed the operation of at least two dehydrogenase enzymes, DH-1 and DH-2, catalysing the (i )-selective oxidation and (S)-selective reduction respectively (Scheme 12). Incubation of cis cycloheptan-l,2-diol afforded only the (S)-2-... 

Bicyclo[3.2.0]heptane-l,5-diols are oxidized by Jead(IV) acetate35,36 or sodium periodate35 to give cycloheptane-1,4-diones. With lead(IV) acetate in acetic acid at 100 C substrates with a hydroxy group in -position to one of the newly formed carbonyl groups eliminate water to afford a,/ -unsaturated cycloheptanediones,36 and / ,y-double bonds migrate to the apposition.35... 

An nnnsnal ring-contraction reaction occnrs on the acid-catalyzed interaction of trimeth-ylhydroqninone 144 with cycloalkane-1,2-diols (e.g. 145) to form the spiro componnds 146 (eqnation 67) . Besides two isomers of cyclohexane-1,2-diols 145, this rearrangement was also described for cyclopentane-, cycloheptane- and cyclooctane-1,2-diols . 

Methylcyclohexanone Diethyl propanedioate Propane-1,2-diol diethanoate Cycloheptane Hept-l-ene Methylcyclohexane Cycloheptanol Heptan-2-one Heptan-3-one Heptan-4-one... 

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