Caged structures prismanes

G. Mehta and co-workers unexpectedly encountered a novel transannular Cannizzaro reaction when 1,4-bishomo-6-seco[7]prismane dialdehyde derivative was subjected to basic conditions to yield a novel octacyclic lactone. " The transannular Cannizzaro reaction is the result of the proximity of the two reacting aldehyde groups induced by the rigid caged structure. 

The polycyclic cage compounds of Group 14 elements heavier than carbon (i.e. tetrahedranes, cubanes, prismanes, etc.) have fascinated chemists for a long time because of their unique structures and expected unusual physico-chemical properties and reactivity1. It was quite reasonable to assume that such exotic compounds could possess properties... 

When the reaction mixture comprising triethylaluminum and phosphaalkyne 9 a (ratio 2 3.5) in n-hexane is allowed to warm from -50°C to room temperature, phosphaalkyne cyclotrimerization with incorporation of two trialkylaluminum units and formation of the bis(homo)prismane 80 (91 %) occurs (Scheme 6-20) [64]. The structure of the cage compound was elucidated unambiguously by crystallography all P-NMR signals appear in the high-field region (6 = -1.2 to -147.3) [64]. 

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