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

3. Allylphosphoramides (CdC−C−N(Me)PO(NMe2)2)
Phosphoramide anion 282 undergoes γ-alkylation
to give 285 with various alkylating agents, 171,172
whereas a mixture of the R- 283 and γ-products 284
is obtained upon treatment with benzophenone. Intramolecular
cyclization of 284 results in the formation
of γ-lactols 287 (Scheme 50). The presence of the
bulky groups on phosphorus in 282 is one possible
reason for the γ-attack by electrophiles. 173 A reaction
of this type has been employed in the synthesis of a
key chiral synthon 286 (δ-valerolactone derivative
which is a Mosquito oviposition attracting pheromone)
(Scheme 50). 174 Replacement of lithium in 282
by magnesium leads almost exclusively to γ-substitution
to give (Z)-enamides. 172,175
Scheme 50
4. 3-Pyrrolines
Lithiated 1-(methoxycarbonyl)-3-pyrroline 288 affords
the R-alkylated product 289 with high regioselectivity;
176 in addition, bisalkylation of 288 yields a
single diastereoisomer 290 with a trans configuration
(Scheme 51). 177 The intermediate anion of 288 is very
reactive and, unless alkylation is carried out immediately
after the anion is formed, it reacts with
another molecule of the starting material to form the
amide 291. 178
Scheme 51
5. N-Nitrosoallylamines (CdC−C−N(NO)R)
The deprotonation of N-nitrosoallylamines, followed
by reaction of 292 with allyl halides, yields
kinetically favored R-adducts 294. Reactions with
carbonyl compounds are reversible thus giving the
γ-E-adducts 293 under thermodynamic control
(Scheme 52). 179
Scheme 52
6. 3-Nitroprop-1-enes (CdC−C−NO2)
Nitropropene 295 undergoes double-deprotonation
to give the dianion 296, which upon treatment with
carbonyl compounds, forms R-nitroallyl alcohols 297
(Scheme 53). 180
Scheme 53
7. N-Allylimines (CdC−C−NdC)
N-Allylimine anions 298 are prepared by deprotonation
of 300. Generally, the reaction of 298 with less
reactive ketones affords regiospecifically the E-γisomer
299, while with more reactive ketones, small
amounts of Z-isomer 301 are also observed together
with the R-adduct 302 (Scheme 54). The reactions of
298 with aldehydes yields mixtures of the R- 302 (R 1
) H) and γ-adducts 299, 301 (R 1 ) H); addition of
HMPA and a low reaction temperature (-78 °C)
favors γ-attack (100% with benzaldehyde). Simply
applying low temperature and apolar solvents (e.g.,
hexane) improves the yield of the R-product. 181 Conversion
of 300 to the boron reagent 303, via γ-attack,
followed by reactions with aldehydes yields the
R-adducts 304 with respect to nitrogen and then the
amine 305 (Scheme 54). 182
8. Bis(trimethylsilyl)allylamines (CdC−C−N(SiMe3)2) and
(Trimethylsilyl)allylamines (CdC−C−NH(SiMe3))
681
Lithiated bis(trimethylsilyl)allylamine 306 gives
(E) γ-adducts 307 and 308 in reactions with alkyl
halides, TMSCl, and carbonyl compounds (Scheme