Premium
Silicon‐Directed Nazarov Reactions III. Stereochemical and Mechanistic Considerations
Author(s) -
Jones Todd K.,
Denmark Scott E.
Publication year - 1983
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.19830660803
Subject(s) - chemistry , steric effects , substituent , ring (chemistry) , stereochemistry , computational chemistry , electronic effect , organic chemistry
The influence of remote substituents on the stereochemical outcome of electrocyclization in the silicon‐directed Nazarov reaction has been examined. While the degree of stereocontrol was modest ( ca. 3:1) the substituent in the major isomer (4,5 or 7‐substituted cis ‐hexahydroind‐2‐en‐1‐ones) is always cis to the protons on the ring fusion. Thorough spectroscopic and conformational analysis revealed that divergent senses of electrocyclization are responsible for the observed products. Additional experiments suggest that steric, rather than stereoelectronic forces control the sense of cyclization. A qualitative description of the nature of reactive intermediates in the silicon‐directed Nazarov reaction is proposed as well as an explanation for the remarkable efficacy of FeCl 3 for inducing the reaction.