Allenylindium chiral

The transmetallations appear to be rapid but the ensuing aldehyde addition is relatively slow. Furthermore, anti adducts of only low or modest ee are obtained. Evidently chiral allenylindium chlorides are more prone to racemize than the corresponding alle-nyltin species. Racemization was less extensive with InBr3 and Inl3 (Table 9.51). 

Table 9.54 Additions of transient chiral allenylindium reagents to representative achiral aldehydes.

Additions of Transient Chiral Allenylindium Reagents To Representative Achiral Aldehydes ... 

The present method is practical and efficient as it employs readily available enantioenriched propargylic alcohols4 as precursors to the allenylindium reagents. With achiral aldehydes the diastereoselectivity is high for branched aldehydes, moderate for unbranched aldehydes, and low for benzaldehyde (Table I).5 With chiral a-methyl aldehydes6 the additions proceed under effective reagent control to afford anti adducts of high ee and with excellent diastereoselectivity (eq. 1 and 2). Comparable results were Obtained with 3 1 dimethyl sulfoxide-tetrahydrofuran (DMSO-THF) as the solvent. 

Marshall, J. A., Johns, B. A. Stereoselective Synthesis of C5-C20 and C21-C34 Subunits of the Core Structure of the Aplyronines. Applications of Enantioselective Additions of Chiral Allenylindium Reagents to Chiral Aldehydes. J. Org. Chem. 2000, 65, 1501-1510,... 

Ohno H, Hamaguchi H, Tanaka T (2001) 2-Ethynylaziridines as Chiral Carbon Nucleophiles Stereoselective Synthesis of 1,3-Amino Alcohols With Three Stereocenters via Allenylindium Reagents Bearing a Protected Amino Group. J Org Chem 66 1867... 

The addition of a chiral allenyl metal to an aldehyde generating a 2-substituted butynyl structure is named Marshall-Tamaru MT) reaction (Scheme 5-13). An allenyl palladium species is generated via a formal Sn2 substitution of the mesylate, which in turn undergoes a transmetalation with diethylzinc yielding a nucleophilic species (Scheme 5-13). The reaction of the electrophile proceeds via a similar -ester enolate transition state as depicted in Scheme 5-13. Corresponding allenylindium reagents can also be used instead of allenylzinc intermediates. ... 

Marshall JA, Palovich MR. Comparative studies on the synthesis of an anti,syn stereotriad with chiral aUenyl-stannane and allenylindium reagents. J. Org. Chem. 1997 62 6001 005. 

Marshall, J.A. and Johns, B.A. (2000) Stereoselective synthesis of C5-C20 and C21-C34 subunits of the core structure of the aplyronines. Applications of enantioselective additions of chiral allenylindium reagents to chiral aldehydes./. Org. Chem., 65, 1501-1510. 

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