Bis-Cyclization-Anion Capture Processes

3 Bis-Cyclization-Anion Capture Processes Allenyl Starter Species 

Oppolzer et al. have utilized the above methodology to synthesize enantiomerically pure (-)a-thujone, using dimethylzinc as the anion capture agent.  

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We have provided numerous examples that show that these bis-cyclization-anion capture processes are diastereoselective. For example, 47a, b in the presence of Pd(0) and 2-thienyl tri-n-butylstannane in THF at 60 °C for 2-A h afford 48 and 49 as single diastereomers (Scheme 5.6.13). ... 

Typical examples of bis-cyclization anion capture processes forming fused and spirocyclic rings, triggered by aryliodide species, are shown in Scheme 5.6.16. Thus, enamide 50 reacts with Af-SEM-indolyl stannane in the presence of Pd(0) to afford a 5 1 diastereomer mixture of 51 and 52 in 74% yield, whilst 53 reacts with 2-pyridyltri- -butyltin in the presence of Pd(0) to afford 54a as a single diastereoisomer. ... 

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