Stereospecific synthesis of P‐epimeric (Rp1, Rp2)‐bis‐[O‐l‐menthylphenylphosphonothionyl] diselenide. A new variant of the stereoselective Staudinger reaction
Abstract:An efficient procedure is described that leads to pure (SP)‐O‐l‐menthylphenylthiophosphinate. The absolute configuration of this diastereomer was assigned by chemical correlation and confirmed by X‐ray crystallography. The reaction of the isomer with phenyl azide, leading to amidate, is a new variant of the stereoselective Staudinger reaction. Addition of elemental selenium to the (SP)‐thiophosphinate led to diastereomeric O‐l‐menthylphenylselenophosphonothioic acid, which was finally oxidized to the diastereo… Show more
“…There is no clear evidence in favor of one particular mechanism. However, the unusual selection in stereospecific synthesis of the P-epimeric of bis[(−)menthyloxyphenylthiophosphoryl)] disulfide and diselenide militates in favor of the first mechanism. , 3 …”
Information stored in the Cambridge Crystallographic
Data Centre shows that anti
−
anti
conformation is
common for bis(organothiophosphoryl) dichalcogenides. In view
of the 1−4 repulsion, the
syn
−
syn
conformation of the SP−X−X4−PS (X
= S and Se) backbone is unfavorable. However, in
compounds
with at least one phenyl group directly bonded to the phosphorus, such
as
bis[tert-butyl(phenyl)thiophosphinyl]
disulfide (Knopik, P. et al. J.
Chem. Soc.,
Dalton Trans.
1993, 2749),
bis(diphenylthiophosphinyl) disulfide
(Gallacher, A. C. et al. Acta Crystallogr.
1993,
C49, 1793) and
bis[tert-butyl(phenyl)thiophosphinyl]
diselenide
(this work) there is the syn
−
syn
geometry caused by the aromatic−aromatic interactions.
Bis[tert-butyl(phenyl)thiophosphinyl] diselenide is monoclinic, space group
C2/c with a = 20.424(2) Å,
b = 9.373(1) Å,
c = 12.907(1) Å, V = 2406.4(2)
Å3, D
c = 1.525 (2)
g/cm3, and Z = 4. Refinement using 2351
reflections
for 118 variables gives R = 0.047. We have used
high-resolution 77Se MAS NMR to study the
structural
properties of the compound. The principal elements
T
ii
of the 77Se
effective dipolar/chemical shift tensor
were calculated from the intensities of the spinning sidebands.
The values of the anisotropy and asymmetry
parameters reflect the distortion of the environment of selenium.
For a series of bis(organothiophosphoryl)
diselenides the T
33 tensor component gives the
largest contribution to the isotropic chemical shifts and
the
span parameter Ω reflects the strength of the diselenide bond.
Molecular packing significantly influences
the intramolecular dynamics of the aliphatic and aromatic groups.
The 13C dipolar dephasing experiment
and line shape analysis of the 1H−H CP/MAS
spectra of selectively 2H-labeled compounds show that
the
phenyl groups are static as a result of the aromatic−aromatic
interaction, while the tert-butyl groups are
under a fast motional regime, with
C
3
v
jumps around the
P−C and C−C bonds.
“…There is no clear evidence in favor of one particular mechanism. However, the unusual selection in stereospecific synthesis of the P-epimeric of bis[(−)menthyloxyphenylthiophosphoryl)] disulfide and diselenide militates in favor of the first mechanism. , 3 …”
Information stored in the Cambridge Crystallographic
Data Centre shows that anti
−
anti
conformation is
common for bis(organothiophosphoryl) dichalcogenides. In view
of the 1−4 repulsion, the
syn
−
syn
conformation of the SP−X−X4−PS (X
= S and Se) backbone is unfavorable. However, in
compounds
with at least one phenyl group directly bonded to the phosphorus, such
as
bis[tert-butyl(phenyl)thiophosphinyl]
disulfide (Knopik, P. et al. J.
Chem. Soc.,
Dalton Trans.
1993, 2749),
bis(diphenylthiophosphinyl) disulfide
(Gallacher, A. C. et al. Acta Crystallogr.
1993,
C49, 1793) and
bis[tert-butyl(phenyl)thiophosphinyl]
diselenide
(this work) there is the syn
−
syn
geometry caused by the aromatic−aromatic interactions.
Bis[tert-butyl(phenyl)thiophosphinyl] diselenide is monoclinic, space group
C2/c with a = 20.424(2) Å,
b = 9.373(1) Å,
c = 12.907(1) Å, V = 2406.4(2)
Å3, D
c = 1.525 (2)
g/cm3, and Z = 4. Refinement using 2351
reflections
for 118 variables gives R = 0.047. We have used
high-resolution 77Se MAS NMR to study the
structural
properties of the compound. The principal elements
T
ii
of the 77Se
effective dipolar/chemical shift tensor
were calculated from the intensities of the spinning sidebands.
The values of the anisotropy and asymmetry
parameters reflect the distortion of the environment of selenium.
For a series of bis(organothiophosphoryl)
diselenides the T
33 tensor component gives the
largest contribution to the isotropic chemical shifts and
the
span parameter Ω reflects the strength of the diselenide bond.
Molecular packing significantly influences
the intramolecular dynamics of the aliphatic and aromatic groups.
The 13C dipolar dephasing experiment
and line shape analysis of the 1H−H CP/MAS
spectra of selectively 2H-labeled compounds show that
the
phenyl groups are static as a result of the aromatic−aromatic
interaction, while the tert-butyl groups are
under a fast motional regime, with
C
3
v
jumps around the
P−C and C−C bonds.
“…inversion of configuration was observed [10]. Direct chlorination of (-)-(S)-26 with thionyl chloride (SOCl 2 ) in dichloromethane (0 -5°C) gave 27 [22] with high yield.…”
Section: Synthesis and Reactions Of Halogenidesmentioning
confidence: 91%
“…The stereoselectivity of the reaction was determined by 1 H NMR spectroscopy via the thiourea derivatives 36 and 37 obtained by addition of (+)-(R)--phenylethylamine (PhEA) to the isothiocyanidates 34 and 35, respectively) [21] (Scheme 21 and 22). The dia- stereoisomeric purity of 34 and 35 was found to be 85% and 76%, respectively, demonstrating high stereoselectivity of both the thiocyanation reactions as well as thiocyanidateisothio-cyanidate isomerisation [22,23].…”
Section: Synthesis and Reactions Of Halogenidesmentioning
confidence: 93%
“…The stereochemistry of the thiocarbonyl fluoride extrusion was investigated with chiral S-trifluoromethyl tbutylphenylphosphinothioate (22) and it was found that most likely the retention of configuration at phosphorus resulted in the 3 22 transformation. It appears that, this model chiral phosphinothioate 22 was stable at elevated temperature (145°C), and just in the presence of a catalytic amount of pyridine, 22 was converted into racemic t-butylphenylphosphinofluoridate (23) with the extrusion of thiocarbonyl fluoride [18] (Scheme 14).…”
Section: Synthesis and Reactions Of Halogenidesmentioning
confidence: 99%
“…It appears that, this model chiral phosphinothioate 22 was stable at elevated temperature (145°C), and just in the presence of a catalytic amount of pyridine, 22 was converted into racemic t-butylphenylphosphinofluoridate (23) with the extrusion of thiocarbonyl fluoride [18] (Scheme 14). …”
Section: Synthesis and Reactions Of Halogenidesmentioning
Basic synthetic procedures commonly applied for the preparation of racemic and optically active phosphinic and phosphinous acid derivatives containing a t-butyl group as a single bulky substituent are presented. Mechanistic and stereochemical aspects of the presented protocols are discussed. Structural studies, which include the X-ray and vibrational circular dichroism-based determinations of the absolute configuration at the stereogenic phosphorus atom and calculations of conformational equilibria for a few model compounds are also mentioned. The use of the optically active tbutylphenylthiophosphinic acid as a chiral solvating agent is illustrated.
A n efficient procedure is described that leads to pure (SJ-0-1-menthylphenylthiophosphinate. The absolute configuration of this diastereomer was assigned by chemical correlation and confirmed by X-ray crystallography. The reaction of the isomer with phenyl azide, leading to amidate, is a new variant of the stereoselective Staudinger reaction. Addition of elemental selenium to the ( Sp)-thiophosphinate led to diastereomeric O-l-menthylphenylselenophosphonothioic acid, which was finally oxidized to the diastereomeric (Rpl ,Rp2)-bis-[0-1-menthylphenylphosphonothionyl] diselenide. The diselenide structure was unambiguously confirmed by 31P NMR spectroscopy.
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