Organotin compounds triflates

The addition of LiCl and Cul, and triphenylarsine as ligand are required to suppress side-reactions in the carbonylative cross-coupling of geminally substituted alkenyl triflate in the synthesis of sarcodictyin. Stereochemical configuration of the double bond of organotin compound was completely lost in this reaction (Equation (5)). " ... 

Stille coupling was also developed in tlie early 1980s and is similar to Suzuki coupling in its sequence. It is used to couple aryl or vinyl halides or triflates with organotin compounds via oxidative addition, transmetallation, and reductive elimination. The oxidative addition reaction has tlie same requirements and preferences as discussed earlier for tlie Heck and Suzuki reactions. The reductive elimination results in formation of tlie new carbon-carbon bond. The main difference is that tlie transmetallation reaction uses an organotin compound and occurs readily without the need for an oxygen base. Aryl, alkenyl, and alkyl stannanes are readily available. Usually only one of tlie groups on tin enters into... 

Organotin compounds can be effectively used as substrates in the palladium-catalyzed cross-coupling reactions of alkenyliodonium salts [66,67]. For example, the reaction of alkenyliodonium triflate 84 with 5-stannylated uracil 83 proceeds smoothly to provide cross-coupled products 87 in moderate yield. The same products 87 are obtained in almost quantitative yield in the palladium-catalyzed cross-coupling of uracil iodonium triflate 85 and vinyltin 86 (Scheme 39) [67]. 

The coupling reaction of aryl and vinyl iodides, bromides, and triflates with organotin compounds can also be very effectively conducted using palladium on carbon as a source of Pd . The yield and rate of... 

Tin hydroxides and oxides are also employed for the syntheses of heteroatom-substituted organotin compounds the treatment of trifluoromethanesulfonic anhydride with bis(trialkyltin)oxides affords trialkyltin triflates (eq (142)) [137] and the reaction of trialkylchlorostannanes with thiols proceeds via trialkylhydroxystannanes to give trialkylstannyl sulfides (eq (143)) [138]. 

Vinyl triflates can be coupled efficiently to various organotin compounds. Further details of this chemistry have now appeared including efficient preparations of trimethylsilyldienes (Scheme 33).71 Two other routes to silyldienes are outlined in Scheme 34. Reduction of allenic alcohols (21) gave moderate yields of the dienyl products, although the stereoselectivity of the process leaves much to be desired. The second method, involving hydroboration of the allene (22) is much more stereoselective and enables either isomer of the final product to be obtained depending on the elimination conditions used. A key application for such dienes is in Diels-Alder reactions, where the products have vinylsilane functionality for further modification. This type of chemistry has now been explored with 2,3-bis(trimethylsilyl)buta-1,... 

Pd-catalyzed coupling of aryl or alkenyl halides and triflates with organotin compounds also takes place smoothly to produce the coupling products, which was discovered by Shlle and Kosugi independently and developed by a number of research groups (Eqs. 5.24 and 25) [100-103],... 

Cross-coupling reactions of aryl (vinyl) halides or triflates with organotin compounds (the Stille reaction) can now be regarded as one of the classical methods of organic synthesis [49]. Again, the basic technique requires palladium complexes with phosphine ligands, and the reactions are carried out in anhydrous organic solvents like DMSO, HMPA, etc., often at elevated temperatures. 

The most important substrates for substitutions of this type are alkenyl and aryl triflates, bromides, or iodides (Sections 16.1-16.4). The most important organometallic compounds to be introduced into the substrates contain Cu, Mg, B, Zn or Sn. The metal-bound C atom can be sp2-, sp2-, or. sp-hybridized in these compounds, and each of these species, in principle, is capable of reacting with unsaturated substrates. Organocopper compounds often (Section 16.1, 16.2), but not always substitute without the need for a catalyst (Section 16.4.5). Grignard compounds substitute in the presence of catalytic amounts of Ni complexes (Section 16.3), while organoboron (Section 16.4.2), organozinc (Section 16.4.3) and organotin (Section 16.4.4) compounds are typically reacted in the presence of Pd complexes (usually Pd(PPhj)4). 

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