Abstract
A domino 1,4-addition/alkyne carbozincation sequence based
on a radical zinc-atom transfer process is disclosed. Two efficient
multicomponent approaches to 3-alkylidenetetrahydrofurans from β-(propargyloxy)enoates
bearing pendant alkynes (including ynamides) have been established:
one involving the direct addition of dialkylzincs, and the second
involving the dimethylzinc-mediated addition of alkyl iodides. Both
sequences utilize the stereoselective formation of intermediate
alkylidenezincs well suited for in situ functionalization
with electrophiles.
1 Introduction
2 1,4-Addition/Cyclization of Dialkylzincs on β-(Propargyloxy)enoates
2.1 β-(Propargyloxy)enoates with a Pendant Terminal
Alkyne
2.2 β-(Propargyloxy)enoates with a Pendant Substituted Alkyne
2.3 β-(Propargyloxy)enoates with a Pendant Ynamide
3 1,4-Addition/Cyclization of Alkylzinc Halides on β-(Propargyloxy)enoates
4 Dialkylzinc-Mediated 1,4-Addition/Cyclization of
Alkyl Iodides on β-(Propargyloxy)enoates
5 Conclusion; Current and Future Work
Key words
zinc - radicals - tandem reaction - alkynes - metalation
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