Rearrangement of Cyclic Allenes via 1,2-Dehydro[10]annulenes: Intramolecular Dehydro Diels-Alder of 3-(Trimethylsilyl)propiolamides

Abstract

Rearrangements of cyclic allenes giving benzo[e]isoindoles were observed when studying intramolecular dehydro Diels-Alder reactions of N-[(3-aryl)propargyl]-3-(trimethylsilyl)propiol­amides.

Key words

allenes - Diels-Alder reactions - annulenes - amides - alkynes

References

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8

Compounds 6a-c were also rather unstable, decomposing rapidly under acidic conditions. In fact, under the Pd-catalyzed coupling conditions both 5 and 6 decomposed slowly, making it necessary to optimize the reaction time. Long reaction times did not afford the desired products.

9

Et₃N favours isomerization of the initial cyclic allene to the corresponding linear aromatic product, thus precluding its rearrangement; see ref. [4]

10

Minor amounts of the benzo[f]isoindol-1-one 2b (10%) and its desilylated derivative (not shown, 9%) were also observed in this case.

11

The E,Z-nomenclature here is correct for 9a and 10a. The nomenclature for 9b (R = OMe) and 9c (R = NO₂) should be 5Z,7E; the nomenclature for 10b (R = OMe) and 10c (R = NO₂) should be 5E,7Z.