Highly efficient biphasic ozonolysis of alkenes using a high-throughput film-shear flow reactor
作者:Alexander J. Kendall、Justin T. Barry、Daniel T. Seidenkranz、Ajay Ryerson、Colin Hiatt、Chase A. Salazar、Dillon J. Bryant、David R. Tyler
DOI:10.1016/j.tetlet.2016.02.042
日期:2016.3
A new method for ozonolysis of alkenes using a continuous flow film-shear reactor was developed. The reactor uses a shearing microfluidic mixing chamber to provide biphasic mixing of an organic phase and aqueous phase with ozone gas. The H2O acts as an in situ reducing agent for the carbonyl oxide intermediate, providing ketones and aldehydes directly from the reaction mixture. Flow rates of up to
Crossed ozonide formation in the ozonolysis of styrene
作者:M. Kimberly Painter、Hyung-Soo Choi、Kurt W. Hillig、Robert L. Kuczkowski
DOI:10.1039/p29860001025
日期:——
Styrene–benzaldehyde mixtures (unsubstituted and the p-nitro, p-chloro, and p-methyl systems) were ozonized in CDCl3 at 0 °C. The yields of styreneozonide and of the two crossed ozonides (stilbene and ethylene ozonides) were determined. The cleavagedirection ratios of the primaryozonides were also determined. In a computer simulation of the yields five rate expressions were employed, giving relative rate coefficient
E1cb mechanism is the overwhelming process in the reaction of bases and ozonides. As a quenching agent in the ozonolysis of a variety of alkenes, the reactions involving triethylamine often gave better yields and proceeded faster than those involving methyl sulfide. On the other hand, in the presence of 4 Å molecular sieves, the secondary amines reacted with mono- and 1,1-di-substituted ozonides to afford
Selectivity in Lewis acid-mediated fragmentations of peroxides and ozonides: application to the synthesis of alkenes, homoallyl ethers, and 1,2-dioxolanes †
作者:Patrick H. Dussault、Hyung-Jae Lee、Xuejun Liu
DOI:10.1039/b001391i
日期:——
Fragmentation of dialkyl peroxides and ozonides is strongly influenced by the choice of Lewis acid. TiCl4 promotes C–O ionization (SN1 reaction) of tertiary peroxides while SnCl4 and BF3·OEt2 promote O–O heterolysis (Hock reaction). The cationic intermediates are trapped with allyltrimethylsilane to afford allylated alkanes and homoallyl ethers. In the absence of a nucleophile, ozonides (1,2,4-trioxolanes) invariably undergo O–O heterolysis. However, the combination of allyltrimethylsilane and SnCl4 results in formation of 1,2-dioxolanes via trapping of intermediates derived from SN1 ionization.
‘Reductive ozonolysis’ via a new fragmentation of carbonyl oxides
作者:Chris Schwartz、Joseph Raible、Kyle Mott、Patrick H. Dussault
DOI:10.1016/j.tet.2006.08.092
日期:2006.11
This account describes the development of methodologies for ‘reductive’ ozonolysis, the direct ozonolytic conversion of alkenes into carbonyl groups without the intermediacy of 1,2,4-trioxolanes (ozonides). Ozonolysis of alkenes in the presence of DMSO produces a mixture of aldehyde and ozonide. The combination of DMSO and Et3N results in improved yields of carbonyls but still leaves unacceptable levels
该文献描述了“还原”臭氧分解方法的发展,即烯烃直接臭氧分解转化为羰基而没有1,2,4-三氧杂环戊烷(臭氧化物)的中介作用。在DMSO存在下烯烃的臭氧分解产生醛和臭氧化物的混合物。DMSO和Et 3 N的组合可提高羰基化合物的收率,但仍然留下不可接受的残留臭氧化物。在不存在DMSO的情况下,使用仲胺或叔胺可获得类似的结果。据认为,胺的影响是由转化成相应的N-氧化物引起的。胺N存在下的臭氧分解氧化物有效抑制臭氧化物的形成,产生高产率的醛。假设与胺氧化物的反应涉及空前的羰基氧化物捕集以产生两性离子加合物,该两性离子加合物断裂以产生所需的羰基,胺和1 O 2。