Abstract:
:A mechanistic study on the nucleophilic substitution of a strictly geometric 21-bromo-3alpha-hydroxyl-3beta-methoxymethyl-5alpha-pregnan-20-one was described. Reaction of the alpha-bromoketone with excess lithium imidazole followed by the addition of extra bases including n-butyllithium, methyllithium, lithium piperidine, and lithium pyrrolidine provided unexpected alpha-nucleophilic carbonyl adducts that derived from strong base. Data from HPLC and proton NMR suggested an epoxide as the intermediate. Two possible reaction pathways were proposed for the nucleophilic substitution reaction. One pathway is the normal SN2 substitution reaction, directly provided the imidazoly product without the formation of the unexpected alpha-substituted products. The other pathway went through an epoxide intermediate, in which imidazole anion or the strong bases added would attack from the less hindered site of the epoxide to give the substitution product.
journal_name
Steroidsjournal_title
Steroidsauthors
Chen CY,Wong FF,Lee YH,Chou SY,Huang JJ,Yeh MYdoi
10.1016/j.steroids.2006.07.004subject
Has Abstractpub_date
2006-11-01 00:00:00pages
942-8issue
11-12eissn
0039-128Xissn
1878-5867pii
S0039-128X(06)00158-9journal_volume
71pub_type
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