Trichloroacetyl-substituted

The biomimetic total synthesis of (+)-20-epiervatamine was accomplished by J. Bosch et al. The authors used the addition of 2-acetylindole enolate to a 3-acylpyridinium salt as akey step to connect the two main fragments. The in situ formed 1,4-dihydropyridine was trapped with trichloroacetic anhydride to afford the corresponding trichloroacetyl-substituted 1,4-dihydropyridine derivative. The conversion of the trichloroacetyl group to a methyl ester was achieved by treatment with sodium methoxide. This transformation can be regarded as the second step of the haloform reaction. 

Substituted (l//,3 -quinazol>ne-2,4-diones 774, as well as the 3-unsubstituted parent compound 774 (R = H), are available by treatment of 2-[(trichloroacetyl)amino]benzamides 772 with sodium hydroxide in DMSO. The reaction proceeds via intermediate isocyanate compounds 773 which undergo ring closure to the final products <20050PP560>. 

The C-acyl heterocycles do not generally form hydrates under acidic or alkaline conditions unless the five-membered ring is also substituted with a second electron-withdrawing group or, as with the trifluoroacetyl and trichloroacetyl derivatives, the carbonyl group is activated to nucleophilic attack. Such activated substituents also undergo the normal reactions with aqueous sodium hydroxide, sodium alkoxide and with amines to give the appropriate... 

Dihydropyridines substituted at the 3- and/or 4-positions undergo selective acylation with trichloroacetic anhydride to give 5-trichloroacetyl-l,4-dihydropyridines 136, which are easily converted by the haloform reaction to esters 137 (Scheme 37) <1998TL9275, 2002T8099, 2003TL4711>. Hydrogenation, over platinum oxide, of... 

The first successful chiral phases used under GC conditions were N-trifluoro-acetyl (TFA)-L-a-amino acid esters. These phases separated race-mates of the more volatile members of the same compounds [33]. Replacing the A-TFA moiety of the selector with trichloroacetyl reduced the enantiose-lectivity by half, while substituting with isobutyryl caused a total loss of the chiral separation. 

Acyl isocyanates are more reactive than alkyl or aryl isocyanates. However, the presence of an additional rr-bond conjugated to the C>i-N bond of the isocyanate opens the possibility for [4 + 2] cycloadditions to compete with normal [2 + 2] additions. Reactions with alkyl and aryl substituted alkenes are rather slow. Propene, tranj-2-butene, styrene and conjugated dienes give only 3-lactams, albeit in moderate yields (Scheme 25). The strained double bond of norbomene, a reactive dienophile, adds across the conjugated 4iT-system of trichloroacetyl isocyanate (equation 51). 

N,N -Bis-(trichloroacetyl)-nylon 6,6 and N,N-bis-(trifluoroacetyl)-nylon 6,6 are prepared by the reaction of the corresponding substituted acetic anhydride with nylon 6,6 These trihalogenoacetyl polyamides are readily soluble in chlorinated hydrocarbon solvents, dioxane, tetrahydrofuran and DMSO. 

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