Deprotonation of Alkoxyallenes and Reaction with Electrophiles Ring-Closing Reactions

Deprotonation of Alkoxyallenes and Reaction with Electrophiles -Ring-Closing Reactions 

Due to the synthetic versatility of donor-substituted allenes, it is of great importance to modify these compounds by substitution reactions at C-l. The CH-acidity at the a-carbon of alkoxyallenes allows their smooth lithiation [12, 42] which conveniently 

The Michael-type addition of 42 to 6ff-l,2-oxazine 52 afforded heterocycle 53 in 45% yield together with bis-adduct 54 as a minor component (Eq. 8.12) [51]. 

In a single reaction, Maas and co-workers used iminium salt 95 as an electrophile for the addition to 1-methoxyallenyl cuprate 94, which was prepared by transmetala-tion of lithiated methoxyallene 42 (Eq. 8.18) [78]. Spiro compound 96 was isolated in moderate yield. 

2 Subsequent Ring-Closing Reactions of the Primary Allene Adducts 

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