Cross-coupling of haloalkynes with organometallic compounds

6 Cross-coupling of Haloalkynes with Organometallic Compounds 

The syn stereoselectivity exhibited the stannylcupration of alkynes is used for the synthesis of stannylated enynes 139 which could be readily transformed to the desired enediynes [67] [Eq. (46)]. 

Using ( )-methylalkenylalanes 140, obtained by highly stereo- and regioselective Zr-catalyzed carboalumination of alkynes, the stereochemically defined enynes 141 can also by synthesized by Pd-catalyzed cross-coupling reactions with 1-haloalkynes [Eq. (47)] [68]. 

Cross-coupling reactions between 1-alkynyl halides and 1-alkenylboranes, which are readily available via hydroboration of alkynes, can also be catalyzed by Pd-phosphine complexes. Stereoselective synthesis of conjugated ( )-enynes 143 was achieved by the coupling of the alkynyl bromide with an alkenylborane [Eq. (48)] [69]. 

In the total synthesis of the strained cyclic enediynes 145, the highly substituted macrocyclic enediyne was constructed by intermolecular two-fold Pd-catalzed coupling of the ,w-di(iodoalkyne) moietes in 144 with m-l,2-bis(trimethylstannyl)ethene in 80% yield [Eq. (49)] [70], 

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Cross-coupling of haloalkynes with organometallic compounds. 222... 

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