HMPA vs. HMPT

[Stephen Yiu Wah Lau]

Jack Kellum (jke...@ucsd.edu) wrote:
: interchangeable? Are their toxicity reasons for using one over the other?

HMPA is very carcinogenic... to remove, I wash everything I
use around HMPA with sat'd CuSO4 solution, to which the HMPA
is supposed to complex to the Cu(II) and render it less toxic
(and wash away into the water)...

--
Stephen Lau --> syw...@ucalgary.ca | Jenny, don't change your
The University of Calgary | number: 867-5309...
Department of Chemistry |
http://www.acs.ucalgary.ca/~sywlau/ | Office: SB429A/437 Lab: SB436
--
Paul J. Franklin (moderator - sci.chem.organic.synthesis)
http://chemistry.gsu.edu/post_docs/koen/wnewshp.html
Georgia State University <che...@panther.gsu.edu>
Atlanta, GA

[Sorin Filip]

Jack Kellum wrote:
>
> I would now like to try a cosolvent to avoid enolate aggregation and
> hopefully increase reactivity of this substitution reaction. I've seen
> references for both HMPA and HMPT as facilitators of this process but I'm
> not sure if one is preferable over the other. Does anyone out there have
> experience/knowledge of the pros and cons of these two compounds? Are they

> interchangeable? Are their toxicity reasons for using one over the other?

> Does one form a more stable/less hindered enolate? Remember, I want
> *di*alkylation, not mono so diastereoselecitivity is not an issue.

Hi Jack! Hi all !

Could you give me some references that you have concerning use of HMPA
or HMPT in enolates chemistry ?

Thanks,
Sorin

[Gabriel Tojo]

Sorin Filip wrote:
>
> Jack Kellum wrote:
> >
> > I would now like to try a cosolvent to avoid enolate aggregation and
> > hopefully increase reactivity of this substitution reaction. I've seen
> > references for both HMPA and HMPT as facilitators of this process but I'm
> > not sure if one is preferable over the other. Does anyone out there have
> > experience/knowledge of the pros and cons of these two compounds? Are they
> > interchangeable? Are their toxicity reasons for using one over the other?
> > Does one form a more stable/less hindered enolate? Remember, I want
> > *di*alkylation, not mono so diastereoselecitivity is not an issue.
>
> Hi Jack! Hi all !
>
> Could you give me some references that you have concerning use of HMPA
> or HMPT in enolates chemistry ?

Hello, Sorin,

There has been a long, confusing, and eventually very informative thread regarding
those two abbreviations.

There is a very common solvent with the formula (Me2N)3P=O, which is called either
HexaMethylPhosphorAmide or HexaMethylPhosphoric Triamide, and is represented by the
abbreviations HMPA and HMPT. This is the molecule that is very commonly used not
only as a solvent, but as a cosolvent to avoid agregation of enolates and other
nucleophiles.

Both abbreviations HMPA and HMPT are very common in the literature, although
Journals tend to prefer HMPA.

There is another molecule with the formula (Me2N)3P, which is called
HexaMethylPhosphorous Triamide. This molecule is an interesting reducing agent which
can be used in a way very similar to Ph3P, for instance, in clorinations with CCl4,
reduction of ozonides and formation of Wittig reagents. The abbreviation most
commonly used for this molecule is HMPT. This is the compound you find under the
abbreviation HMPT in the Aldrich and Lancaster catalogues. This compound is useless
as a cosolvent.

The abbreviation HMPT is used both for (Me2N)3P=O and (Me2N)3P, and most times when
you find HMPT in the literature you need to infer its nature from the chemistry
involved.

In fact, (Me2N)3P=O is used much more often than (Me2N)3P. Thus, most times when you
read an article HMPT representes the solvent (HMPA), but when you decide to check
the structure or buy it, you find (Me2N)3P in the chemistry catalogues.

This led to many organic chemists to wrongly believe that (Me2N)3P is an interesting
cosolvent that can be used similarly to (Me2N)3P=O, and this belief even
contaminated highly reputed organic textbooks like Smith´s "Organic Synthesis"

I hope to have disentangled the whole thing.

I am collecting cases in which this confusion is reported in the literature and I
would appreciate any help.

--
Gabriel Tojo
Profesor Titular de Quimica Organica
Royal University of Santiago de Compostela
SPAIN

[Jack Kellum]

Sorin,

See the following:

1) Piers; Tet. Lett.; 1984; 3155
2) Cregge; Tet. Lett.; 1973; 2425
3) Marczak; Tet. Lett.; 1993; V34; 6627
4) Chapdelaine; Org. React.; 1990; V38; 225
5) Odic; J. Organomet. Chem.; 1973; V55; 273 --in French
6) Sowinski; J. Org. Chem.; 1979; V44; 2369
7) Pfeffer; J. Org. Chem.; 1970; V35; 262
8) Smrekar; Chimia; 1985; V39; 147
9) Mukhopadhyay; Helv. Chim. Acta; 1982; V115; 1705 --discusses use of DMPU
in place of HMPA
10) Tsushima; Chem. Lett.; 1989; 1313
11) Naef; Angew. Chem., Int. Ed. Engl.; 1981; V20; 1030
12) Seebach; Chem. Ber.; 1982; V115; 1705

Usage seems to vary from catalytic to stoichiometric to 3:1 THF/HMPA.
Probably need to try several conditions.

Jack

Sorin Filip <so...@organik.orgchem.uni-leipzig.de> wrote in message
news:7l00bp$m...@panther.Gsu.EDU...

>
> Jack Kellum wrote:
> >
> > I would now like to try a cosolvent to avoid enolate aggregation and
> > hopefully increase reactivity of this substitution reaction. I've seen
> > references for both HMPA and HMPT as facilitators of this process but
I'm
> > not sure if one is preferable over the other. Does anyone out there
have
> > experience/knowledge of the pros and cons of these two compounds? Are
they
> > interchangeable? Are their toxicity reasons for using one over the
other?
> > Does one form a more stable/less hindered enolate? Remember, I want
> > *di*alkylation, not mono so diastereoselecitivity is not an issue.
>
>
>
>
>
> Hi Jack! Hi all !
>
> Could you give me some references that you have concerning use of HMPA
> or HMPT in enolates chemistry ?
>

> Thanks,
> Sorin