Pentadienyl amino

The scope of allylic electrophiles that react with amines was shown to encompass electron-neutral and electron-rich ciimamyl methyl carbonates, as well as furan-2-yl and alkyl-substituted allylic methyl carbonates. An ort/io-substituted cinnamyl carbonate was found to react with lower enantioselectivity, a trend that has been observed in later studies of reactions with other nucleophiles. The electron-poor p-nitrocinnamyl carbonate also reacted, but with reduced enantioselectivity. Allylic amination of dienyl carbonates also occur in some cases with high selectivity for formation of the product with the amino group at the y-position over the s-position of the pentadienyl unit [66]. Arylamines did not react with allylic carbonates under these conditions. However, they have been shown to react in the presence of the metalacyclic iridium-phosphoramidite catalysts that are discussed in Sect. 4. 

Figure 11.3. SHMO frontier orbitals and total energies for amino-substituted pentadienyl cations.

X is NR R2. The substituent is converted to a Z substituent via the low-lying a orbital, and the ring is deactivated toward further electrophilic attack. The ortho and para channels lead to products. The interaction diagram for an X -substituted pentadienyl cation, substituted in the 1-, 2-, and 3-positions, as models of the transition states for the ortho, meta, and para channels, are too complex to draw simple conclusions. The HOMO and LUMO of the three pentadienyl cations with an amino substituent are shown in Figure 11.3. Notice that the LUMO of each is suitable to activate the C—H bond at the saturated site toward abstraction by the base. Curiously, the meta cation has the lowest LUMO and should most readily eliminate the proton. The stabilities of the transition states should be in the order of the Hiickel n energies. These are 6a — 8.7621/ , 6a — 8.499 / , and 6a — 8.718 / , respectively. Thus the ortho and para channels are favored over the meta channel, and the ortho route is slightly preferred over the para route. Experimentally, para substitution products are often the major ones in spite of there being two ortho pathways. The predominance of para products is usually attributed to steric effects. 

Hexen 3-Hydroximino-l-phenyl-El4b, 313 (aus En —on) Hydroxylamin N-Methyl-N-(5-phenyl-2,4-pentadienyl)- E16a, 313 (Amino-oxid-Umlager.)... 

ReN202PC34Hj2, Rhenium, (V-cyclopenta-dienyl) ( 1 -(1-naphthal-enyl)ethyl] amino]caibonyl] nitrosyl(tri-phenylphosphine)-, (+)-(SR)-, 29 217 ReOjCjHs, Rhenium, tricarbonyl(Ti -cyclo-pentadienyl)-, 29 211... 

Cl 2H18CI4CUN4OS, Thiamine tetrachlorocuprate, 40B, 553 Cl2H18N2O3S, 2,3-Dihydro-2-acetyl-3,3-dimethyl-4 [(lE)-4-methyl-1,3-pentadienyll l,2,5-thiadiazole 1,1-dioxide, 46B, 403 C12H18N4O3S, 2,7-Dimethylthiachromine-8-ethanol dihydrate, 40B, 350 Cl2H19N2O4PS, N-(2,6-Dimethylphenyl)-2-amino-5,6-dihydro-4H-1,3-thiazine phosphate, 45B, 429... 

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