Isobutylmagnesium chloride

Hydromagnesiation (11, 163-164 12, 168-169). Cp2TiCl2-catalyzed syn-addition of isobutylmagnesium chloride to propargylic alcohols affords a stereoselective route to vinylmagnesium chlorides for further synthetic use. ... 

A 500 ml three-necked flask is fitted with a pressure-equalizing dropping funnel and a stopper, and furnished with a magnetic stirrer bar and an inert atmosphere. Isobutylmagnesium chloride (0.75 M in ether, 320 mol, 240 mmol) is placed in the flask and cooled by means of an ice-water bath. Dicyclopentadienyltitanium dichloride (1.3 g, 5.2 mmol) is added, and the solution is stirred at 0° for 10 min. A solution of oct-2-yn-l-ol (13.2 g, 105 mmol) is added to the cooled solution dropwise from the dropping funnel during 20 min, and the resulting solution is stirred at room temperature for 4 h. 

A solution of isobutylmagnesium chloride is obtained from isobutyl chloride and magnesium turnings in ether. Determine its concentration by titration before use. 

Carbohydrates are important chiral, non-racemic precursors (chiral templates) to statine and its derivatives. Aldehyde 6.138 0 as converted to alcohol 6.139 by reaction with isobutylmagnesium bromide. After conversion to a benzoate (6.140), displacement with sodium azide gave 6.141. The tetrahydrofuran ring was opened and oxidation gave 6.142. Oxidation of the aldehyde and then reduction of the azide moiety led to (+)-statine (3R,4S-tf.P5). Reaction of 6.139 with mesyl chloride and then sodium benzoate gave the benzoate (6.140) of opposite absolute configuration, which was converted to (-)-statine (3S,4R-t. 95) by the same sequence. 

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