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Synthesis of Enantiomerically Pure Carbohydrate‐Derived Annulated Cyclopentadienes and Ferrocenes
Author(s) -
Li Zhi,
Vasella Andrea
Publication year - 1996
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19960790815
Subject(s) - chemistry , ferrocene , yield (engineering) , thermal decomposition , structural isomer , medicinal chemistry , organic chemistry , carbohydrate , derivative (finance) , electrochemistry , electrode , materials science , economics , financial economics , metallurgy
The cyclopentadienes 3a/b/c, 8b/c, 12a/b/d , and 16a/b/d were prepared as mixtures of regioisomers from the D ‐mannitol‐derivatives 1,6,10 , and 14 and transformed into the ferrocenes 17, 18 , and 19 (73%; 38:17:45), 23, 24 , and 25 (70%; 6:42 :52), 26 (31%), and 27 (27%), respectively. Deprotection of 17–19 with HCl/MeOH gave the H 2 O‐soluble ferrocenes 20–22 ; chloromercuration and iodination of 17 via 29 led to the C 2 ‐symmetric diiodo‐ferrocene 30 . The mono(chloromercurio) derivative 28 , obtained as a by‐product, was also transformed into 29 . The structure of the ferrocenes 18 and 19 , and of the bis(chloromercurio)ferrocene 29 has been established by X‐ray analysis. The starting cyclopentadienes 3 were obtained in 50% yield from 1 by dialkylation of CpNa, followed by thermolysis of the spiro‐annulated 2 . Similarly, dimesylate 6 (from 4 ) gave the spiro‐annulated diene 7 and the annulated dienes 8 in about equal amounts; thermolysis transformed 7 into 8 (62%). The dienes 12 were prepared in 15% yield from the ditriflate 10 via 11 , the dimesylate 9 proving insufficiently reactive, and the dienes 16 (49%) from 14 via 15 .