Crotylzincation alkynes

It is also possible to achieve the formation of five-membered rings by coupling the allylzincation of a metallated alkyne with an intramolecular nucleophilic substitution. Thus, allylzincation of the ethylzinc alkynylide generated from 5-iodo-l-pentyne (66)45, or direct treatment of the latter with excess crotylzinc chloride177, led to the alkenyl... 

Nevertheless, chiral propargylic amines remain interesting substrates for achieving the diastereoselective addition of substituted allylic organozinc compounds to metallated alkynes. Besides crotylzincation, one example of diastereoselective addition of zincated allyl ethyl ether to 328 has also been reported183. 

---