Pyridyl stannanes

Butyl(tri-2-pyridyl)stannane can be prepared from 2-lithiopyridine and butyltin trichloride and also from the reaction of 2-lithiopyridine with stannocene. The product acts as a tridentate ligand, and the complexes with Li+ Mo(CO)3, and W(CO)3 have been characterized (Equation (57)). 

Butyllithium reagents, with chromium, 5, 382 Butyl(tri-2-pyridyl)stannane, preparation, 3, 827 ft-Butylvanadium(III) complex, preparation, 5, 19... 

Pyridyl stannanes have seen use in the transformation of 250 into 251. These dinucleating phenanthroline-based ligands have found utility in the synthesis of bimetallic complexes [91]. 

Derivatives of cephalosporins can serve as selective class C P-lactamase inhibitors and therefore routes to their preparation are of value [101]. Pyridyl analog 287 could be prepared in one of two ways, which differed only in the nature of the reacting partners. p-Lactam stannane 286 could be coupled with pyridyl bromide 19 to afford 287. Alternatively, pyridyl stannane 236 was reacted with bromide 288 to generate 287. 

Both 2- and 3-pyridyl stannanes can be prepared by palladium-catalysed stannylation. The M-oxides and qnatemary salts of pyridyl stannanes can be used in Stille couplings. ... 

Boron-substituted pyridine reagents can be used to construct the bipyridine ring system by coupling them with halopyridines in the presence of a Pd° catalyst and a base (Suzuki method). Various ligands have been made in this manner in moderate to high yields, including 2,3-bipyridine (85%)41 and 3,5-dimethyl bipyridine (60%) 42 One valuable feature of the Suzuki method is that it is compatible with stannanes. A pyridyl diethylborane has been coupled to a tributyl tin-functionalized pyridyl bromide.43 This compatibility is useful for polypyridine syntheses because subsequent Stille coupling of the bipyridyl stannane is possible. 

In addition to the hnear array of pyridyl rings, it was also possible to construct cyclic arrays as in cyclosexipyridine 262 [94], This was accomplished by sequential Stille couplings initiated by reacting 258 with 259 to afford 260. The remaining bromide of 260 was then coupled with a vinyl stannane derivative that produced 261. Unmasking of the latent carbonyl functionality preceded elaboration to 262. 

Stille coupling with aryl tris-(perfluorohexylethyl)stannane as a reaction component (aryls also comprise furyl and pyridyl) [65,66]. 

The product alkyl-2-pyridyl sulfides are of synthetic interest by virtue of their ability to form a chelated lithio anion for reaction with carbon electrophiles. Subsequent removal of the sulfide can then be achieved using either nickel boride or tri- -butyl stannane [4] (Scheme 8). 

The triflate leaving group was introduced to coupling reactions as an alterative to halogens. They are particularly useful when there is no simple way to prepare the required halide partner. Aryl triflates can be prepared from phenols and pyridyl triflates can be prepared from pyridones. This transformation is usually achieved using triflic anhydride and an amine base. The coupling of a triflate 2.191, derived from quinolone 2.190, with stannane 2.192 was used in a short synthesis of dubamine 2.193 (Scheme 2.66). 

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