Diverging pathways to topologically complex polycyclic bis-acetals and their ring system interchange.

Carbinol-tethered octalin-diols (1), which differ only by the C11 configuration at the angular position, were transformed selectively to three types of structurally unrelated original scaffolds such as unsymmetrical octahydroanthracenes (5/7), furofuranes (6), or spirans (8/9) via a two-step protocol. The 11S* configuration ensures a C13-C4 Friedel-Crafts type C-C bonding (through an unprecedented oxidative cleavage-triggered domino process) while the 11R* configuration allows for a C13-C2 Marson-type Friedel-Crafts C-C bonding (through a nucleophilic acetal opening).

Competing domino processes: path-discriminating ability of epoxide stereochemistry at the angular position.

Structurally different products can be reached selectively from unsaturated vicinal bicyclic diols, which differ only by the epoxide configuration at the angular position. It is possible to modify the regiochemical outcome of the domino process in such a way as to create a different pathway, [4 + 2] versus [4 + 3 + 2], and control product distribution by using the configuration bias. No previous example of a domino variant of the [4 + 3 + 2] process appears to have been documented.

Microwave-accelerated competing domino processes: a tether-controlled dual pathway into high molecular complexity.

Bicyclic unsaturated diols undergo a path selective modular domino transformation upon subjection to Pb(OAc)4, the reaction being biased to the nature of the angular substituent. The magnitude of the linking chain and the nature of the angular substituent determine the reaction course. Methylene ether linkage acts as an autoremovable directing group (ring-retained domino product 5), whereas a propylene linkage switches the path toward the ring-expanded type 21 domino product.

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

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.