2-Alkoxyallylboronates, addition

The two-carbon chain elongation of protected D-glyceraldehyde (R)-24 and (R)-62 can be realized via ( -7-alkoxyallylboronate additions, followed by alkene ozonolysis. The allylboronate 162 generated in situ adds to (R)-62 giving a single stereoisomer 163, which can be converted to D-arabinose derivatives following ozonolysis (Scheme 13.57). Similarly, 164 added to (R)-24 gave a major adduct 165 that was then converted into 2-0-methyl-D-arabinose derivatives [105]. 

Two-carbon chain elongation of protected D-glyceraldebyde R)-37 and R)-99 can be realized via ( )-)/-alkoxyallylboronate additions, followed by alkene ozonolysis, furnishing D-arabi-nose derivatives [300]. 

The superacid CF3S03H2+-B(0S02CF3)4 was shown to catalyze the addition of allylsilanes to aldehydes and cyclohexanone to form homoallylic alcohols913 (CH2C12 solvent, room temperature, 60-95% yields). 2-Alkoxyallylboronates add... 

Several additional chiral type I and III allyl metal reagents based on boron,chromium, and titaniumhave been reported. The most selective of these are the chiral 7-alkoxyallylboronate (231) developed by Wuts for application in a synthesis of (-)-ejco-brevicomin, and the allyltin reagent gener-... 

Synthesis from o-mannitol The AB ring of sesbanimide was also synthesized from cyclohexyhdene D-glyceraldehyde 57, readily available from D-mannitol (Scheme 8). ° The addition of (Z)-7-alkoxyallylboronate 56, prepared from 55, to 57... 

As exemplified with 23, the highly regioselective platinum-catalyzed hydroboration of alkoxy-substituted allenes with pinacolborane provided the corresponding 2)-y-alkoxyallylboronates by total anti-Markovnikov addition at the terminal double bond (Equation 12) [45]. Alkyl- and aryl-substituted allenes devoid of an alkoxy group, how-... 

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