Carbon-tin bond formation

Unsymmetrical functional tetraorganotins are generally prepared by tin hydride addition (hydrostaimation) to functional unsaturated organic compounds (88) (see Hydroboration). The realization that organotin hydrides readily add to atiphatic carbon—carbon double and triple bonds forming tin—carbon bonds led to a synthetic method which does not rely on reactive organometatiic reagents for tin—carbon bond formation and, thus, allows the synthesis of... 

Bishomoallyl alcohols, via allyindium reagents, 9, 703 Bis(hydrostannation), in tin-carbon bond formation, 3, 814 Bis(imidazolyl) ligands, chromium complexes, 5, 359 Bis(imido) systems, with chromium(VI), as models, 5, 377 Bis(imido)tungsten complexes, synthesis, 5, 749 Bis(imido)uranium(VI) complexes, synthesis, 4, 216-217 Bis(imino)carbenes, with Zr(IV), 4, 798 Bis(iminooxazolidine) complexes, biaryl-bridged, with Zr(IV) and Hf(IV), 4, 811-812... 

Metalloorganic liquids, characteristics, 1, 853 Metallopolymers, with n-coordinated metals, 12, 311 Metallosilanes, preparation methods, 3, 521 Metallostannation, in tin-carbon bond formation, 3, 817 Metal-metal bonds... 

Direct metallation of o-halogenophenoxyelement derivatives of silicon, tin, and phosphorus leads to an unstable metallated intermediate which undergoes a rapid 1,3-rearrangement under element-carbon bond formation. This type of reaction seems to be a general method for the synthesis of hydroxyphenyl element derivatives [1-4], We have studied the influence of different organoelement groups on the reaction pathway. The yield increases in the sequence R3Sn < R2P < RjSi P(0)(0R)2. 

General methods for the formation of a tin-alkenyl bond are described in Section 3. This section considers only those reactions in which the tin-carbon bond is already formed, and the alkenyl group is generated by modification of the organic group that is already present. 

Carbon-carbon bond formation has also been achieved using electroauxiliaries. The method developed by Yoshida and coworkers uses an auxiliary (silicon, tin, sulfur), which when added to a molecule, decreases the oxidation potential of the starting compound. Thus the chance of overoxidation can be avoided. The anodic oxidation of compounds having a... 

Isotopic labelling, Eq. (49), indicated that the transmetalation occurs via direct tin-carbon bond cleavage rather than via intermediate formation of an alkoxy-cyclopropane [45],... 

The relative weakness of the carbon-tin bond provided a useful method for carbon-carbon bond formation by cross-coupling reaction with acyl halides. This reaction has been applied for the two-step synthesis of a-ketocyclopropyl sulfones (equation 8)30. 

Tin-carbon bonds in [(CO)sMnSnMe3] are cleaved by LiAlH4 or NaBH4 to form hydrides and the reaction of CF3COCI and HSiCl3 with the same compound results in the formation of [(CO)sMnSnMe2Cl]373. 

Tin enolates are one of the most versatile reagents for carbon-carbon bond formation. They are used either in ionic or radical reaction manner. Organotin enolates exist as equilibrium mixtures of keto and/or enol forms, and their ratio largely depends on their substituents and conditions (Equation (66)).220 In general, an enol form has high nucleo-philicity in ionic system and thus only the enol form is often shown in a reaction scheme. 

Chiral metal alkoxides M(OR)4 have been developed as asymmetric variants of ordinary Lewis acids, such as A1C13 and ZrCU, and are used as catalysts for selective carbon-carbon bond formation. Thus, starting from bidentate l,l -bi-2-naphthol derivatives (BINOL) and SnCU, a series of chiral tin(iv) aryloxides 221 (Figure 7) was prepared and successfully applied to the enantioselective Diels-Alder reaction <2006TL873>. Similar silocanes obtained from menthone- or camphor-derived 2,2 -biphenols have been obtained and their configuration was analyzed by NOE differential spectroscopy (NOEDS) <1997JOC7156>. 

First, the utility of organostannyl compounds for generating carbo-cations or carbon radicals is discussed. Oxidation of organostannyl compounds such as a-stannyl sulfides, amines, esters, and ethers with metallic oxidants or photochemical methods gives their cation radicals, from which carbocations and carbon radicals are generated by cleavage of the carbon-tin bond. These reactive intermediates are employed for carbon-carbon bond formation, particularly in intermo-lecular reactions. 

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