3-Hexyne reagent treatment

Better results can be obtained by generating the boronate species with the aid of sodium methoxide. In this case, satisfactory transmetalation occurs on treatment with Cul. Thus, the functionalized copper reagent 55 can be alkynylated with 1-bromo-l-hexyne at —40 °C, furnishing the enyne 56 in 75% yield (Scheme 2.15) [32]. 

Allylethylzinc A reagent (2) of this type is prepared by hydroboration of 1-hexyne with dicyclohcxylborane (1 cquiv.) to form an (E)-l-alkcnylboranc 1, which undergoes transmctalation to form 2 on treatment with diethylzinc. This reagent adds to an aldehyde in the presence of the catalyst (-)-3-ejco-(dimethylamino)isoborneol (DAIB, 3) to form a secondary (E)-allylic alcohol in 70-95% yield with 79-98% cc. 

Bongini and coworkers converted an Amberlyst bromide into the perbromide by treatment with a carbon tetrachloride solution of bromine. On storage, only a small decrease in active bromine content was observed. This reagent converted phenylacetylene dissolved in dichloromethane, to an approximately 1 3 cisItransmiyXmQ of the 1,2-dibromo addition product in 92% yield at room temperature in 1 h. A similar result was obtained with 1-hexyne, although the reaction required refluxing for 3h. When the Amberlyst bromide had been treated with a dichloromethane solution of chlorine, the polymer acted as a chlorobromination agent. 

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