Organotin phosphinates

The preparation and reactions of organotin phosphines continue to attract interest, and have been reviewed. Cyclodehydrogenation of the secondary phosphine (40) with azobenzene in the presence of AIBN gives the 1,2-stannaphospholans (41). Radical-initiated addition of di-n-butylstannane to the dialkynylphosphines... 

Organotin phosphines, arsines, stibines and bismuthines are known, and are exemplified, together with some of the commoner organotin amines in Table 10. 

The palladium-catalyzed coupling of aiyl and vinyl halides to organotin compounds, known as Stille coupling, is one of the most important catalytic methods of carbon-carbon bond formation. The reaction is generally conducted in polar organic solvents, such as dimethylformamide, with tertiary phosphine complexes of palladium, although phosphine-free complexes or simple Pd-salts are also frequently used as catalysts [8]. 

Several important improvements of this methodology have been reported since 1994. A broad range of organotins were used in the reactions with aryl-, heteroaryl-, or alkenyliodonium salts in aqueous organic solvents. This reaction (Equation (2)) takes place at room temperature in the presence of phosphine-free palladium... 

The reaction of isoprene with C02 in the presence of organotin ethoxide and DBU by the use of dicyclohexyl(/3-pyridylethyl)phosphine (106) affords the isomeric esters 107 and 108 by head-to-tail and tail-to-tail dimerizations. Tin ethoxide forms tin carbonate, which seems to be an effective carrier of C0 [100],... 

Lately, a number of papers have dealt with microwave-assisted reactions on palladium-doped A1203. Villemin reported on Stifle, Suzuki, Heck and Trost—Tsuji reactions where potassium fluoride on alumina was used as the base26. The reactions were carried out without solvent or stabilising phosphine ligands in single-mode reactors. The Stifle reactions were noteworthy as the toxic organotin residue remained adsorbed on the solid support, thus allowing a simplified work-up procedure for the otherwise unpleasant, and toxic, stannous by-products. Both the Stifle and the Suzuki reactions could be performed under air. Furthermore, it was noted that with experiments where the... 

Despite the many phosphine/palladium systems developed for the coupling of organohalides with organotin compounds [117-119], this reaction re-... 

An example that used this protocol the substrate of which contains a sensitive functionality is depicted in Scheme 45 [202]. 1,3-Diene monoepoxide is easily attacked by a palladium(O) complex to form the corresponding 7r-allylpalladium species. Thus such a process could be banished from the desired selective transformation as depicted in Scheme 46 by the employment of the alkynyltin reagent with an aid of triphenylarsine ligand [203]. Organotin protocol is also convenient for introduction of a small alkynyl moiety such as C2 or C3 or preparation of symmetrical diarylethynes (Scheme 47) [204]. Shirakawa et al. reported recently that iminophosphine 4 is much more effective ligand for palladium than tris(2-furyl)phosphine in this reaction (Scheme 48) [32,205]. 

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