Allenylindium reagents

Scheme 2.50 Palladium-catalyzed coupling of allenylindium reagents with aryl iodides.

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

Table 9.55 Additions of silylated and non-silylated allenylindium reagents to achiral aldehydes.

Sulfonic amides of alkynylaziridines can also be converted to allenylindium reagents by oxidative transmetallation of transient allenylpalladium complexes. When the reaction is perfomed in the presence of an aldehyde the expected adducts are produced stereoselectively (Eq. 9.150) [120],... 

Table 9.56 In situ formation of allenylindium reagents from trans-alkynylaziridines...

SYNTHESIS AND UTILIZATION OF INDIUM (I) IODIDE FOR IN SITU FORMATION OF ENANTIOENRICHED ALLENYLINDIUM REAGENTS AND THEIR ADDITION TO ALDEHYDES (2R,3S,4S)-1-(tert-BUTYLDIPHENYLSILYLOXY)-2,4-DIMETHYL-5-HEXYN-3-OL [5-Hexyn-3-ol, 1-[[(1,1-dimethylethyl)diphenylsilyl]oxy]-2,4-dimethyl-,... 

The present method is practical and efficient as it employs readily available enantioenriched propargylic alcohols 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). With cHral a-methyl aldehydes 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. 

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

A unique reaction of allenylindium reagents, prepared from propargyl bromides and indium, and haloazines gives rise to the appropriate allenyl-azines. Although the reaction is not a Heck coupling, but a cross-coupling reaction, the aryl moiety is formally attached to a carbon-carbon multiple bond, therefore we mention it here. 

Synthesis and Utilization of Ini for in situ Formation of Enantioenriched Allenylindium Reagents and Their Addition to Aldehydes (2R,3S,4S)-1-(tert-Butyldiphenylsilyloxy)-2,4-dimethyl-5-hexyn-3-ol. 

Allenylindium reagents, generated in situ from the reaction of indium with propargyl bromides, can be employed as effective cross-coupling partners in palladium-catalyzed reactions with a variety of organic electrophiles to produce substituted allenes, polyallenes, unsymmetrical bisallenes in excellent yields (Table 22).358... 

Table 22 Synthesis of allenes via allenylindium reagents. Reproduced with permission from Wiles...

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,... 

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 and co-workers have demonstrated that allenylindium [277] and allen-ylzinc [276] reagents can be formed in situ from propargyl mesylate 389 and that these reagents react enantioselectively with aldehydes without additional Lewis acid catalysis (Scheme 11-28). The allenylzinc and allenylindium reagents 392 and 391 are derived from the allenylpalladium intermediate 390 via metathesis with Et2Zn and Ini, respectively. Allenylpalladium intermediate 390 in turn is derived from (7 )-389 via invertive displacement of the mesylate functionality of 389 with Pd(0). 

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. 

Johns BA, Grant CM, Marshall JA. Synthesis and utilization of indium (1) iodide for in situ formation of enantioenriched allenylindium reagents and their addition to aldehydes 2R, 35,45)-1 -(tert-butyldiphenylsilyloxy )-2,4-dimethyl-5-hexyn-3-ol. Org. Synt. 2003 79 59-66. 

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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