Allenyltin reagents

The enantiomerically enriched allenic and propargylic boron reagents A and C have been prepared by treatment of the (R,R)-bromoboron intermediate B with the appropriate propargyl or allenyltin reagent [24]. Allenic and propargylic adducts are... 

In the coupling of Z-3-iodo-3-trimethylsilylacrylic acid and allenyltin reagents the carbon-carbon bond was established in a Stille coupling, followed by the attack of the carboxylic acid on the allene moiety, probably promoted by palladium (4.39.). 

The preparation of allenylindium reagents and their reaction with aldehydes has further expanded the utility of indium in synthesis. By making use of the transmetallation protocol, enantiomerically enriched allenyltin reagents 308 (themselves generated by an anti Sn2 substitution of propargylic mesylate 307 with... 

Marshall JA, Palovich MR. Synthesis of stereopentad subunits of zincophorin and rifamycin S through use of chiral allenyltin reagents. 7. Org. Chem. 1998 63(ll) 3701-3705. 

These mesylates, in turn, can be converted to enantioenriched allenyltin, zinc, and indium reagents which add to aldehydes with excellent diastereo-and enantioselectivity to afford either syn- or anti-homopropargylic alcohols or allenylcarbinols (eq 2, 3, and 4).3 4 Adducts of this type serve as useful intermediates for the synthesis of polyketide and hydrofuran natural products.5... 

Some related reagent, the 2,4-pentadienyltin, was shown to be reactive as well [304]. Propargyltin was equally found to be efficient for transferring an allene group [305]. However, a larger excess of propargyltin is needed, due to the radical isomerization of the propargyltin to the less reactive allenyltin. This was used in the synthesis of modified nucleosides [306]. 

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