6280-00-8Relevant academic research and scientific papers
Cobalt(II)-Catalyzed Stereoselective Olefin Isomerization: Facile Access to Acyclic Trisubstituted Alkenes
Zhang, Sheng,Bedi, Deepika,Cheng, Lu,Unruh, Daniel K.,Li, Guigen,Findlater, Michael
supporting information, p. 8910 - 8917 (2020/12/23)
Stereoselective synthesis of trisubstituted alkenes is a long-standing challenge in organic chemistry, due to the small energy differences between E and Z isomers of trisubstituted alkenes (compared with 1,2-disubstituted alkenes). Transition metal-catalyzed isomerization of 1,1-disubstituted alkenes can serve as an alternative approach to trisubstituted alkenes, but it remains underdeveloped owing to issues relating to reaction efficiency and stereoselectivity. Here we show that a novel cobalt catalyst can overcome these challenges to provide an efficient and stereoselective access to a broad range of trisubstituted alkenes. This protocol is compatible with both mono- and dienes and exhibits a good functional group tolerance and scalability. Moreover, it has proven to be a useful tool to construct organic luminophores and a deuterated trisubstituted alkene. A preliminary study of the mechanism suggests that a cobalt-hydride pathway is involved in the reaction. The high stereoselectivity of the reaction is attributed to both a π-πstacking effect and the steric hindrance between substrate and catalyst.
Rhodium-Catalyzed Room Temperature C-C Activation of Cyclopropanol for One-Step Access to Diverse 1,6-Diketones
Ghosh, Asit,Pati, Bedadyuti Vedvyas,Ravikumar, P. C.
supporting information, (2020/04/02)
A rhodium-catalyzed room temperature C-C activation of cyclopropanol has been demonstrated for the single-step synthesis of a range of electronically and sterically distinct 1,6-diketones. This reaction proceeds efficiently in shorter reaction time following a highly atom-economical pathway. To illustrate the synthetic potential of 1,6-diketones, aldol and macrocyclization reactions have been successfully demonstrated. Preliminary mechanistic studies revealed the involvement of nonradical pathways.
One-pot synthesis and characterization of some new types of 5,5′-disubstituted bis(imidazolidine-2,4-diones)
Khodaee, Ziba,Yahyazadeh, Asieh,Mahmoodi, Nosrat O.
, p. 288 - 292 (2013/06/04)
The synthesis and structural elucidation of some novel 5,5′- disubstituted spiro and nonspiro-bis-hydantoins are reported. The Bucherer Burge's method has been modified for the preparation of some 5,5′-substituted bis(imidazolidine-2,4-dione) derivatives starting with diketones (1-5) and dialdehydes (6, 7). In some cases, diastereoisomeric mixtures of compounds were obtained. The resulting bis-hydantoins (8-11, 13, 14) have not to our knowledge been previously reported in the literature.
Reactions of 1,2-diketones with vinyllithium: Addition reactions and dianionic oxy Cope rearrangements of cyclic and acyclic substrates
Clausen, Christian,Wartchow, Rudolf,Butenschoen, Holger
, p. 93 - 113 (2007/10/03)
Dianionic oxy Cope rearrangements have been shown to take place at low temperature upon syn double addition of alkenyllithium derivatives to cyclobutanedione compounds such as benzocyclobutenedione chromium complex 1 or squaric acid esters. In order to obtain some insight into the more general applicability of this type of reaction sequence beyond these special cases, a number of 1,2-diketones were treated with vinyllithium. The diketones tested include benzil derivatives, aliphatic acyclic 1,2-diketones, ortho-quinones, and cyclic aliphatic 1,2-diketones. With benzil and heterobenzil derivatives, the desired double addition/dianionic oxy Cope rearrangement was found to take place at low temperature, leading to 1,6-diketones and their intramolecular aldol adducts in up to 80% overall yield. With acyclic aliphatic 1,2-diketones as substrates, this reaction sequence was also found, albeit with somewhat lower yields and requiring higher temperatures than in the benzil cases. A brief investigation of the intramolecular aldol adduct/1,6-hexanedione equilibrium indicated that the preferential formation of intramolecular aldol adducts at lower temperatures and at shorter reaction times appears to be the result of kinetic reaction control, whereas the preference for 1,6-diketones at higher temperatures is caused by thermodynamic reaction control, ortho-Quinones reacted with vinyllithium only by addition; no dianionic oxy Cope rearrangement was observed. This was also the case for most aliphatic cyclic diketones; however, in the case of 1,2-indanedione, rearrangement products were obtained in moderate yield at elevated reaction temperatures.
Photoinduced Electron Transfer (PET) cyclization and photooxygenation of 2,6-diaryl-1,6-heptadienes and 2,7-diaryl-1,7-octadienes
Griesbeck, Axel G.,Sadlek, Oliver,Polborn, Kurt
, p. 545 - 549 (2007/10/03)
The 2,6-diaryl-substituted 1,6-heptadienes 3a-c and the 2,7-diaryl-substituted 1,7-octadienes 4a-b were cleanly converted into the corresponding anellated cyclobutanes 5 and 6, resp., when irradiated under photoelectron-transfer conditions (9,10-dicyanoanthracene in acetonitrile). Only for 4c did the rearranged compound 7c become the dominant photoproduct. Oxygen trapping experiments with formation of endoperoxides 8, 9 were successful in the case of the electron-rich substrates 3b, c and 4c. VCH Verlagsgesellschaft mbH, 1996.
Conjugate addition of allylic groups to α,β-unsaturated carbonyl compounds via (η3-allyl)Fe(CO)2NO complexes
Itoh, Keiji,Nakanishi, Saburo,Otsuji, Yoshio
, p. 215 - 224 (2007/10/02)
(η3-Allyl)Fe(CO)2NO complexes undergo conjugate addition to α,β-unsaturated carbonyl compounds to give the corresponding δ,ε-unsaturated carbonyl compounds in good yields.The reaction of (η3-1- or 2-trimethylsiloxyallyl)Fe(CO)2NO complexes with α,β-unsaturated ketones affords 1,6- or 1,5-diketones, respectively. (η3-1-Acetonylallyl)Fe(CO)2NO complexes also react with α,β-unsaturated carbonyl compounds to give 1,8-dicarbonyl compounds.The mechanisms and reactivity of these conjugate addition reactions are discussed.Key words: Iron; Carbonyl; Allyl; Silicon; Nitrosyl; Ketone
