6252-18-2Relevant academic research and scientific papers
Synthesis of Tertiary Benzylic Nitriles via Nickel-Catalyzed Markovnikov Hydrocyanation of α-Substituted Styrenes
Xing, Yidan,Yu, Rongrong,Fang, Xianjie
supporting information, p. 1008 - 1012 (2020/02/04)
The Markovnikov hydrocyanation of α-substituted styrenes enables the synthesis of tertiary benzylic nitriles under nickel catalysis. The Lewis-acid-free transformation features an unprecedented functional groups tolerance, including the-OH and-NH2 groups. A broad range of tertiary benzylic nitriles were obtained in good to excellent yields. In addition, an asymmetric version of this reaction was preliminarily investigated.
Cationic Co(I)-intermediates for hydrofunctionalization reactions: Regio- A nd enantioselective cobalt-catalyzed 1,2-hydroboration of 1,3-dienes
Duvvuri, Krishnaja,Dewese, Kendra R.,Parsutkar, Mahesh M.,Jing, Stanley M.,Mehta, Milauni M.,Gallucci, Judith C.,Rajanbabu
, p. 7365 - 7375 (2019/05/16)
Much of the recent work on catalytic hydroboration of alkenes has focused on simple alkenes and styrene derivatives with few examples of reactions of 1,3-dienes, which have been reported to undergo mostly 1,4-additions to give allylic boronates. We find that reduced cobalt catalysts generated from 1,n-bis-diphenylphosphinoalkane complexes [Ph2P-(CH2)n-PPh2]CoX2; n = 1-5) or from (2-oxazolinyl)phenyldiarylphosphine complexes [(G-PHOX)CoX2] (G = 4-substituent on oxazoline ring) effect selective 1,2-, 1,4-, or 4,3-additions of pinacolborane (HBPin) to a variety of 1,3-dienes depending on the ligands chosen. Conditions have been found to optimize the 1,2-additions. The reactive catalysts can be generated from the cobalt(II)-complexes using trimethylaluminum, methyl aluminoxane, or activated zinc in the presence of sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate (NaBARF). The complex, (dppp)CoCl2, gives the best results (ratio of 1,2-to 1,4-addition >95:5) for a variety of linear terminal 1,3-dienes and 2-substituted 1,3-dienes. The [(PHOX)CoX2] (X = Cl, Br) complexes give mostly 1,4-addition with linear unsubstituted 1,3-dienes, but, surprisingly, selective 1,2-additions with 2-substituted or 2,3-disubstituted 1,3-dienes. Isolated and fully characterized (X-ray crystallography) Co(I)-complexes, (dppp)3Co2Cl2 and [(S,S)-BDPP]3Co2Cl2, do not catalyze the reaction unless activated by a Lewis acid or NaBARF, suggesting a key role for a cationic Co(I) species in the catalytic cycle. Regio- A nd enantioselective 1,2-hydroborations of 2-substituted 1,3-dienes are best accomplished using a catalyst prepared via activation of a chiral phosphinooxazoline-cobalt(II) complex with zinc and NaBARF. A number of common functional groups, among them,-OBn,-OTBS,-OTs, N-phthalimido-groups, are tolerated, and er's > 95:5 are obtained for several dienes including 1-alkenylcycloalk-1-enes. This operationally simple reaction expands the realm of asymmetric hydroboration to provide direct access to a number of nearly enantiopure homoallylic boronates, which are not readily accessible by current methods. The resulting boronates have been converted into the corresponding alcohols, potassium trifluororoborate salts, N-BOC amines, and aryl derivatives by C-BPin to C-aryl transformation.
Diels-Alder reactions of masked o-benzoquinones with 1-vinylcyclohexenes: A short and efficient entry to highly functionalized decahydrophenanthrene skeleton
Niu, Guang-Hao,Hou, Chieh-Shen,Chuang, Gary Jing,Wu, Chi-Phi,Liao, Chun-Chen
supporting information, p. 3794 - 3801 (2014/06/24)
Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding cycloaddition products, that is, decahydrophenanthrenes along with bicyclo[2.2.2]octenones. In the former case, the MOBs serve as the dienophile, and in the later case, the 1-vinylcyclohexenes act as the dienophile. The obtained bicyclo[2.2.2]octenones could be transformed into the corresponding decahydrophenanthrenes through a Cope rearrangement at 220 °C. Thus, these tandem reactions provide a short and efficient entry to the decahydrophenanthrene skeleton from easily available 2-methoxyphenols. Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding decahydrophenanthrenes and bicyclo[2.2.2]octenones. The obtained bicyclo[2.2.2]octenones could be transformed into decahydrophenanthrenes through a Cope rearrangement at 220 °C. Copyright
Formation and [3,3]-sigmatropic rearrangement of O-allyl nitronic esters: A new route to γ,δ-unsaturated nitro compounds
Wade, Peter A.,Pipic, Alma,Santhanaraman, Manikandan,Le, Hung T.
supporting information; experimental part, p. 3531 - 3532 (2009/12/03)
O-Allyl nitronic esters that are obtained from tin(iv) catalyzed Diels-Alder reactions undergo thermal rearrangement to γ,δ- unsaturated nitro compounds.
Alkylidenation of carbonyl compounds with gem-dizincioalkanes mediated with titanium dichloride
Matsubara, Seijiro,Mizuno, Tsuyoshi,Otake, Tasuyuiki,Kobata, Masami,Utimoto, Kiitiro,Takai, Kazuhiko
, p. 1369 - 1371 (2007/10/03)
Olefination of carbonyl compounds with gem-dizincio-alkanes, bis(iodozincio)methane, 1,1-bis(iodozincio)ethane, and bis(bromozincio)methyltrimethylsilane, afforded the corresponding olefins in good to excellent yields.
Photooxygenation of 1-Vinylcycloalkenes. The Competition between "Ene" Reaction and Cycloaddition of Singlet Oxygen
Herz, Werner,Juo, Rouh-Rong
, p. 618 - 627 (2007/10/02)
The competition between the "ene" reaction and 1,4-cycloaddition reaction of 1O2 in a series of 1-vinylcycloalkenes (n = 5-10, 12) and 1-isopropenylcycloalkenes (n = 6-8) was studied.Ring size had a profound effect.When n = 5 or 7, products of the "ene" reaction predominated, but as ring size increased cycloaddition competed closely with the "ene" process, the crossover being at ring size 10. 1-Vinylhexenes constituted an exception with 1,4-cycloaddition greatly predominant. "Ene" products were almost exclusively conjugated diene hydroperoxides or secondary products derived from them; small amounts of unconjugated diene hydroperoxides were formed only when n = 9, 10, or 12.The influence of ring size of the "ene" to cycloaddition product ratio is compared with the rates of photooxygenation and the degree of syn-regiospecificity exhibited by (Z)-1-methylcycloalkenes and attributed to the same mainly conformational factors, as is the geometry of the "ene" products.The 1,4-cycloaddition products were converted to furans by means of ferrous sulfate.
Lewis Acid Mediated Reactions of Organocopper Reagents. Entrainment in the Conjugate Addition to α,β-Unsaturated Ketones, Esters, and Acids via the RCu*BF3 System
Yamamoto, Yoshinori,Yamamoto, Sinichi,Yatagai, Hidetaka,Ishihara, Yuji,Maruyama, Kazuhiro
, p. 119 - 126 (2007/10/02)
Lewis acid mediated reactions of organocopper reagents with various kinds of α,β-unsaturated carbonyl derivatives are described.RCu*BF3, as well as RCu-other Lewis acid systems, is useful for the conjugate addition to the α,β-unsaturated ketones and esters, whose double bonds are sterically crowded.Certain α,β-unsaturated carboxylic acids also undergo a 1,4-addition through this reagent.Methyl sorbate undergos a 1,4-addition via BuCu*BF3, while undergoing a 1,6-α,δ-addition via Bu2CuLi.BuCu*BF3 reacts more readily with an aldehyde than with a ketone; the degree of chemoselectivity is greater than that of Bu2CuLi, BuLi, or BuMgBr.The R2CuLi-BF3 system is useful for the double alkylation of α,β-unsaturated esters at the β-position and the carbonyl center.Stereochemical aspects of these new copper reagents are also reported.
