Trimethylstannane

Stannanes also add across double bonds offiuonnated olefins in a free radical reaction Trimethylstannane undergoes stereospecific addition to hexafluorocyclo-butene to afford trans 1,2,3,3,4,4 hexafluoro 1 (trimethylstannyl)cyclobutane [5] (equation 1)... 

The Suzuki reaction was also used to prepare the polyketone since this particular reaction tolerates the subsequent step (Scheme 6.19).135 Palladium-catalyzed cross-coupling of aromatic diacid chlorides and bis(trimethylstannane) monomers was utilized to prepare poly(arylene ether ketone)s.136... 

Diethylamino)trimethylstannane is a colorless liquid which boils at 36°/6 mm. The compound is quickly hydrolyzed by moisture. The proton nuclear magnetic resonance spectrum of a neat sample shows a CH3—Sn resonance at 9.92 r with HChs—Sn119 splitting of 56.5 cycles and HCh,—Sn117 splitting of 54.0 cycles. The ethyl resonance consists of a triplet at 9.10 r... 

Whether SnFLt is a symmetric or spherical top was discussed based on the rotational spectrum of the sixth stretching vibrational overtone, obtained by photoacoustic spectroscopy107. The IR band at vgn ]q 1844 cm-1 served to investigate the kinetics and mechanism of chemical vapour deposition of a thin tin layer, by thermolysis of trimethylstannane at 378-503 K108. 

The third methodology in pyridylstannane synthesis is unique to 2,6-dihalopyridines whose synthesis using the conventional lithiation method is low-yielding (17% yield) [57]. Schubert et al. prepared 2,6-bis(trimethyltin)pyridine (70) via an SnAt displacement of 2,6-dichloropyridine with sodium trimethylstannane, derived in situ from trimethyltin chloride [58-60]. 

The retrosynthesis involves the following transformations i) isomerisation of the endocyclic doble bond to the exo position ii) substitution of the terminal methylene group by a more stable carbonyl group (retro-Wittig reaction) iii) nucleophilic retro-Michael addition iv) reductive allylic rearrangement v) dealkylation of tertiary alcohol vi) homolytic cleavage and functionalisation vii) dehydroiodination viii) conversion of ethynyl ketone to carboxylic acid derivative ix) homolytic cleavage and functionalisation x) 3-bromo-debutylation xi) conversion of vinyl trimethylstannane to methyl 2-oxocyclopentanecarboxylate (67). 

The synthesis of modhephene (54), which proceeds according to plan in an overall yield of >16%, with complete control of relative stereochemistry, demonstrates the ability of radical cyclisations to form propellane systems and generate highly crowded neopentyl quaternary centres. The accepted pathway for the cyclisation of the vinyl trimethylstannane is shown in Scheme 7.25. The chair-like transition state in which the methyl substituent on the radical is pseudoequatorial, accounts for the observed endo stereoselectivity. 

Mixed trialkylstannyl and silyl derivatives have also been used in coupling reactions, with subsequent replacement of the silyl substituent by bromine, leading to species that are capable of undergoing further coupling reactions. This process was amply demonstrated by the recent synthesis of micrococcinic acid 203, which involved four palladium-catalyzed crosscoupling reactions on stannylated substrates, two palladium-catalyzed trimethylstannane replacements of bromine, two trimethylsilyl displacements by bromine, and a total of four bromine-lithium exchange reactions, on three different thiazole derivatives and one pyridine derivative (91-TL4263). 

Conversely, inversion was observed during stannylation of the a-lithio compound with chloro-trimethylstannane. This provides the (S)-enantiomer of the chiral a-lithio compound, from the same precursor, by a stannylation destannylation sequence5. 

Electrochemical studies of (menthyloxymethyl)trimethylstannane (250)206 reveals an oxidation potential of 1.09 V, which is lower than the corresponding silane 246 and germane 245 and the parent 247. The oxidation potential of tetrabutylstannane 251 was determined to be 1.52 V, which is higher than the alkoxystannane 250 thus the decrease in the oxidation potential for 250 was attributed to the Gc Sn-n0 interaction. It can be argued that the oc Sn-n0 interaction raises the energy of the... 

The gas-phase acidity of some of the simplest organogermanes and of trimethylstannane have been determined by a combination of gas-phase equilibrium measurements and proton-transfer bracketing experiments using FTMS185 190. The experimental values of A//°cjd are shown in Table 6 and refer to the enthalpy change associated with reaction 29. 

Similar results are found with 2-allyloxy-l-chloro-naphthalene, that affords the diphenylphosphine (98% yield) and trimethylstannane (84% yield) of (l,2-dihydro-naphtho[2,l-Z>]furan-l-ylmethyl) derivatives. 

Dinitrobiphenyl was prepared by another approach from (3,3-dinitrodiphenyl)-iodonium bisulphate and (3-nitrophenyl)trimethylstannane (85%) with palladium catalysis the same salt with tetramethyltin afforded 3-nitrotoluene (77%), whereas dibenziodolium tetrafluoroborate was converted into 2,2,-dimethylbiphenyl [37] ... 

The trimethylstannanes, on the other hand (which can be transmetallated at -120 °C in methyl THF) each give a ratio of products reflecting the stereochemistry of the starting material. The stereospecificity of the reactions indicates considerable configurational stability in these a-seleno organolithiums at -120 °C. The same ratios are obtained after 3 h or 6 h, indicating that the epimerisation takes place during the exothermic addition of the methyllithium. 

Methyl trimethylstannyl tellurium was obtained when trimethylstannane reacted with methyl bis[trifluoromethyl]phosphano or -arsano tellurium2,3.The products were not isolated but identified by NMR spectroscopy. 

Dimethyl ditellurium and trimethylstannane at 20° quantitatively formed methyl trimeth-ylstannyl tellurium, according to an NMR spectroscopic investigation2. 

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