Exploring modular domino reactions: competing processes based on the nature of the angular substituent.

ABSTRACT

The octaline diol system 6 was found to undergo an interesting set of reactions upon treatment with PhI(OAc)2, leading, in a single synthetic operation, to complex oxygen heterocycles. Experimental evidence supports an intramolecular hetero[4 + 2 + 2] adduct that has heretofore never been observed, which completely dominates the hetero[4 + 2] path in several cases. The domino protocol can be biased one way or another depending on both the nature of the pi-system and the length of the methylene spacer at the angular position.