From: Chapman, Robert D (ChapmanRD$##$navair.navy.mil)
Date: Thu Mar 09 2000 - 12:52:39 EST
Kocienski ("Protecting Groups") writes: "...there is little distinction in
the ease of formation or hydrolytic stability of cyclic
S,S-acetals...compared with acyclic congeners." He also cites a review on
thioacetals for protection: Groebel, B.T.; Seebach, D. Synthesis 1977, 357.
Kocienski gives an example of an acyclic dithioacetal cleaved by AgNO3. Is
that better for you?
Robert D. Chapman, Ph.D.
Chemistry & Materials Division (Code 4T4200D)
Naval Air Warfare Center
China Lake, CA 93555 USA
> ----------
> From: Jack Kellum
> Reply To: Jack Kellum
> Sent: March 9, 2000 9:17 AM
> To: Multiple recipients of list orglist
> Subject: ORGLIST: thioacetal cleavage
>
> Upon consulting Greene's book on protective groups, I see that cyclic
> thioacetals (formed from aldehyde + ethane dithiol) can be cleaved with
> mercury (II) perchlorate. OTOH, acyclic thioacetals (formed from aldehyde
> +
> ethanethiol) are shown to be cleaved with a mix of mercury (II) chloride
> and
> mercury (II) oxide. Is it reasonable to assume that the acyclic
> dithioacetal will cleave with mercury (II) perchlorate? Is it six of one
> and half a dozen of the other with respect to the two sets of conditions
> effecting essentially the same cleavage? The reason I ask is that I have
> on
> hand ethanethiol and mercury (II) perchlorate, but no EDT or other mercury
> salts. I would think that the important thing is that mercury (II) is
> present, and less important is the counterion. Any thoughts? Yeah, yeah,
> I
> can always try the reaction on small scale and see if it works but before
> I
> start generating mercury waste I'd like some informed opinions first.
>
> Also, has anyone ever cleaved an acyclic dithioacetal with NBS? What
> might
> the advantages/disadvantages be with the use of this reagent besides
> avoiding the highly toxic mercury or silver salts usually employed in
> these
> conditions?
>
> Thanks in advance for all relevant responses.
>
> Jack
>
>
>
>
>
>
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