Regioselectivity of the Reactions of Heteroatom-Stabilized Allyl ...

710
Scheme 165 Scheme 167
properties have been discussed in the light of ab initio
model calculations. 403
The structure of an allylic sulfone [PhSO2CH(CHd
CH2)Li‚diglyme]2 849 (Scheme 165) was investigated
in solution and in the crystal by Gais et al. 404 The
crystalline material was obtained from the corresponding
allyl phenyl sulfone by metalation with
n BuLi in diglyme. The X-ray structure 849 shows a
dimeric species in which the S-O-Li subunits form
an eight membered ring. The Li + is coordinated by
one sulfur oxygen atom and two diglyme oxygens, the
anionic C(R) is not involved in the coordination
system. 13 C and 1 H NMR data of 849 in THF-d8 at
25 °C of this compound were interpreted in terms of
a vinyl-substituted R-sulfonyl carbanion with a Li +
gegenion.
2. Oxygen
The X-ray structure has been discussed of allyl
vinyl ether 850 (Scheme 166). This species belongs
to the interesting class of metalated allyl derivatives
and undergoes the so-called “Carbanion Accelerated
Claisen Rearrangement” to give 851 (Scheme 166). 405
Scheme 166
3. Nitrogen
The reactions of lithiated allyldiphenylamine 852
with (+)- or (-)-B-methoxydiisopinocamphylborane
[(Ipc)2B(OMe), 853] give the corresponding (E)-aminoallyl
boranes (cf. 854 from (-)-B-853). Compounds
854 are useful reagents for the synthesis of 3-(diphenylamino)-4-hydroxyalkenes
855 (after reaction with
a variety of aldehydes and conventional workup).
Compounds 855 are chiral at the C4-center, the
configuration of this carbon was determined by the
X-ray structure of the corresponding Mosher ester
856 (Scheme 167). 164
A comparable pathway leads to anti-�-hydroxy
amines 861 via anti-�-diphenylimino alcohols (e.g.,
as the X-rayed example 860a, Scheme 167). 182 In
addition to diphenylamines, allyldiphenylimines have
also been metalated and derivatives 857 reacted with
(Ipc)2B-Cl (858) to give intermediates 859. After
reaction with aldehydes 859 were transformed to
�-hydroxy(diphenylmethylene)amino alcohols 860
which finally gave, after conventional workup and
deprotection, with high or complete stereocontrol, the
anti-�-hydroxy amines target molecules 861.
The crystal structure of a chiral 1-aminoallyllithium
derivative, the dimeric (3S)-3-lithio-1-[(S)-2-
(methoxymethyl)pyrrolidino]-1,3-diphenylpropene 862
(Scheme 167), 406 obtained from its aminoallyl precursor
and n BuLi/hexane in toluene at 0 °C, reveals
interesting characteristics. The 1-aminoallyl group
is nearly planar, the nitrogen atom is pyramidal with
the lone pair directed toward the allyl moiety. The
bond angles and interatomic distances indicate that
the lithium is coordinated to the γ-center. The
remaining coordination site of the metal cation is
occupied by the benzyl group of the second monomeric
moiety.
4. Phosphorus
The lithiated chiral 2-propenylphosphonamide species
(cf. 863, Scheme 168) 219 is an easily accessible
reagent for the stereoselective 1,4-addition to ethyl
3,4,5,6-tetrahydro-4-oxo-pyridine-1-carboxylate.
Scheme 168 shows the resulting product 864, for
which an X-ray structure is available.
Scheme 168
The X-ray structure is also available of the vinyl
phosphine oxide 865 (Scheme 169) which is a useful
allylmetal precursor in a multistep synthesis of