1002-53-5Relevant articles and documents
Alternating polystannanes: Syntheses and properties
Harrypersad, Shane,Foucher, Daniel
, p. 7120 - 7123 (2015)
A new condensation polymerization route leading to alternating polystannanes is presented. The stoichiometric reaction of tin dihydrides and tin diamides in diethyl ether or toluene under mild reaction conditions afforded three new moderate molecular weig
Metal-Catalyzed Dehydropolymerization of Secondary Stannanes to High Molecular Weight Polystannanes
Imori, Toru,Lu, Victor,Cai, Hui,Tilley, T. Don
, p. 9931 - 9940 (1995)
The first high molecular weight polystannanes, H(SnR2)nH (R = nBu, nHex, nOct), result from dehydropolymerization of secondary stannanes R2SnH2 by zirconocene catalysts.Good catalysts include zirconocenes based on both CpCp*Zr (Cp* = η5-C5Me5) and Cp2Zr fragments, and the most active catalyst with respect to production of high molecular weight polystannanes was Me2C(η5-C5H4)2ZrMe.The latter catalyst produced H(SnnBu2)nH chains (Mw/Mn = 66 900/20 300) that were contaminated by ca. 18percent (by weight) low molecular weight cyclic oligomers.Lower molecular weights resulted from dehydropolymerizations of Me2SnH2, PhMeSnH2, and Ph2SnH2.At room temperature, H(SnR2)nH (R = alkyl group) polystannanes have λmax values at ca. 380-400 nm, attributed to ? --> ?* transitions.Thermal gravimetric analyses on the polystannanes reveal that these polymers are as thermally stable as related poly(dialkylsilane)s and have onset temperatures for thermal decomposition in the range 200-270 deg C, under both nitrogen and air.The H(SnnBu2)nH polymer has been shown to be a good precursor to SnO2, as shown by bulk pyrolysis in air (ceramic yield: 56percent).Preliminary results also indicate that these polymers may be useful as precursors to elemental tin.The polystannanes are photosensitive, and their photobleaching behavior has been characterized by UV-vis spectrometry and 119Sn NMR spectroscopy, which demonstrated that H(SnnBu2)nH is photochemically depolymerized to a 2:1 mixture of cyclo-(SnnBu2)5 and cyclo-(SnnBu2)6.The polymers H(SnnHex2)nH and H(SnnOct2)nH exhibit thermochromic behavior which is visibly evident as a discoloration from yellow to colorless upon warming above room temperature.This reversible behavior is associated with an abrupt change in λmax (e.g., from 402 to 378 nm for films of H(SnnOct2)nH) and a phase change at ca. 40 deg C (by differential scanning calorimetry).Thin films of H(SnnBu2)nH and H(SnnOct2)nH on glass slides were doped by exposure to SbF5 vapor to conductivities of 10-2 and 0.3 S cm-1, respectively.Preliminary experiments suggest that the dehydropolymerization occurs by a ?-bond metathesis mechanism involving four-center transition states.A previous report on production of high molecular weight poly(dibutylstannane) by the reductive coupling of nBu2SnCl2 by Na/15-crown-5 was reinvestigated and found to produce only low molecular weight material with Mw/Mn = 2400/1200.
Transition-Metal-Free Coupling Reaction of Vinylcyclopropanes with Aldehydes Catalyzed by Tin Hydride
Ieki, Ryosuke,Kani, Yuria,Tsunoi, Shinji,Shibata, Ikuya
, p. 6295 - 6300 (2015)
Donor-acceptor cyclopropanes are useful building blocks for catalytic cycloaddition reactions with a range of electrophiles to give various cyclic products. In contrast, relatively few methods are available for the synthesis of homoallylic alcohols through coupling of vinylcyclopropanes (VCPs) with aldehydes, even with transition-metal catalysts. Here, we report that the hydrostannation of vinylcyclopropanes (VCPs) was effectively promoted by dibutyliodotin hydride (Bu2SnIH). The resultant allylic tin compounds reacted easily with aldehydes. Furthermore, the use of Bu2SnIH was effectively catalytic in the presence of hydrosilane as a hydride source, which established a coupling reaction of VCPs with aldehydes for the synthesis of homoallylic alcohols without the use of transition-metal catalysts. In contrast to conventional catalytic reactions of VCPs, the presented method allowed the use of several VCPs in addition to conventional donor-acceptor cyclopropanes.
A convenient route to distannanes, oligostannanes, and polystannanes
Khan, Aman,Gossage, Robert A.,Foucher, Daniel A.
, p. 1046 - 1052 (2010)
The quantitative conversion of the tertiary stannane (ν;-Bu) 3SnH (2) into (ν-Bu)6Sn2 (4) was achieved by heating the neat hydride material under low pressure or under closed inert atmosphere conditions. A 31% conversion of Ph3SnH (3)to Ph6Sn 2 (5) was also observed under low pressure; however, under closed inert atmosphere conditions afforded Ph4Sn (6) as the major product. A mixed distannane, (ν-Bu)3SnSnPh3 (7), can also be prepared in good yield utilizing an equal molar ratio of 2 and 3 and the same reaction conditions used to prepare 4. This solvent-free, catalyst-free route to distannanes was extended to a secondary stannane, (ν-Bu)2SnH 2 (8), which yielded evidence (NMR) for hydride terminated distannane H(ν-Bu)2SnSn(ν-Bu)2H(9), the polystannane [(ν-Bu)2Sn] ' (10), and various cyclic stannanes [(ν- Bu)2Sn]ν=5,6=5,6 (11, 12). Further evidence for 10 was afforded by gel permeation chromatography (GPC) where a broad, moderate molecular weight, but highly dispersed polymer, was obtained (Mw = 1.8 × 104 Da, polydispersity index (PDI) = 6.9) and a characteristic UV-vis absorbance (1max)of ν370 nm observed.
PREPARATIONS OF META-IODOBENZYLGUANIDINE AND PRECURSORS THEREOF
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Paragraph 0135; 0136-0138, (2021/06/25)
The present disclosure provides purified forms of iobenguane and preparations of a precursor to iobenguane, such as a polymer, the polymer comprising a monomer of formula (I) or a pharmaceutically acceptable salt thereof, the preparation comprising leacha
PREPARATIONS OF META-IODOBENZYLGUANIDINE AND PRECURSORS THEREOF
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, (2016/05/19)
The present disclosure provides purified forms of iobenguane and preparations of a precursor to iobenguane, such as a polymer, the polymer comprising a monomer of formula (I) or a pharmaceutically acceptable salt thereof, the preparation comprising leachable tin at a level of 0 ppm to 850 ppm.
