Aldehydes alkynyl boranes

In the hydroboration of terminal alkenes, carrying a ketone or aldehyde group, with a variety of borane reagents, dicyclohexylborane has been identified as the most efficient reagent. Analogous hydroboration of alkynyl ketones and alkynyl aldehydes with dicyclohexylborane yields the corresponding olefinic carbonyl compounds after protonation, or dicarbonyl compounds after oxidation. ... 

Corey and Cimprich have used acetylenic dimethylborane as the nucleophile for the asymmetric addition of acetylenic nucleophiles to aldehydes. This reagent was generated in sitn from the corresponding alkynyl stannane and bromodimethylborane (Scheme 21.12). A typical procedure involved addition of a solution of bromodimethyl-borane in methylcyclohexane to a solution of the alkynyl stannane (1.3 to 1.5) in toluene at -78°C. A solntion of the oxazaborolidine (0.25 to 1 equiv in toluene) was added after 30 minntes, and after an additional 15 minntes the aldehyde was added. The chiral... 

Hydroboration of 1-bromo-l-alkynes with chloro(thexyl)-borane leads to the synthesis of alkynyl ketones in 61-63% yields by the sequence of reactions shown in eq 5. Sequential treatment of alkenylchloro(thexyl)boranes, which are formed by the reaction of chloro(thexyl)borane with alkynes, with lithium chloro-propargylide and aldehydes affords 1,3-enynols or 1,2,4-trienols depending on the reaction conditions. ... 

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