Comment on hydroxyselenation paper

Jo Sweeney (sweeneyjb@siva.bristol.ac.uk)
Mon, 19 Jun 95 15:19:11 0000

Dear Jonathan,
Thanks for your comments, which I think are spot on! The pseudoanomeric
effect will only be felt in the pseudoaxially-conformed species, thus one
could explain the difference by invoking Curtin-Hammett. There is certainly
NMR evidence for the predominance of pseudoaxial acetate in
acetoxycyclohexene
The really meaty questions, however, are -
-Why there should be no face selectivity in selenenonium ion, when there is
exclusive face control in iodination? and
-Why isn't there an NGP ring-opening of the alpha-selenenonium ion, as
postulated for the iodination? If this occured, the process would be
inherently more rapid beecause of its intramolecularity, and should lead to
a predominance of the 1,2-dioxygenated system, assuming formation of
selenenonium ion is not rate-determining.
The most obvious answer to these questions is that the RDS in
hydroxyselenation is ring-opening, whereas in hydroxyiodination it is
formation of iodonium ion.
I think!
I have to say that the main problem with this work is that one can
imediately think of several hundred experiments to do, most of which are
conceptually very simple. Unfortunately for a graduate student, even the
simplest reaction has finite (and frequently not small) time demands! This
project could take 200 man-years to sort satisfactorily!
Thanks for your comments.
Jo

Dr. J.B. Sweeney,
School of Chemistry,
University of Bristol,
Cantock's Close,
Bristol
BS8 1TS
UK

Tel. +44 117 928 8165
FACS. +44 117 929 8611

ECTOC-1. Conference home page: http://www.ch.ic.ac.uk/ectoc/ using
Netscape, Mosaic, etc.
E-mail discussions: http://www.ch.ic.ac.uk/hypermail/ectoc/
To unsubscribe from this list, send the message UNSUBSCRIBE ECTOC to
listserver@ic.ac.uk