6493-83-0Relevant academic research and scientific papers
Rapid, One-Step Synthesis of α-Ketoacetals via Electrophilic Etherification
Paris, Timothy J.,Schwartz, Chris,Sundall, Eric,Willand-Charnley, Rachel
, p. 14797 - 14811 (2021/10/20)
Herein, we report a rapid, one-step synthesis of α-ketoacetals via electrophilic etherification of α-alkoxy enolates and monoperoxyacetals. Methyl, primary, and secondary α-ketoacetals were obtained in 44-63% yields from tetrahydropyranyl substrates; usin
Tandem Acid/Pd-Catalyzed Reductive Rearrangement of Glycol Derivatives
Ciszek, Benjamin,Fleischer, Ivana,Kathe, Prasad,Schmidt, Tanno A.
supporting information, p. 3641 - 3646 (2020/03/25)
Herein, we describe the acid/Pd-tandem-catalyzed transformation of glycol derivatives into terminal formic esters. Mechanistic investigations show that the substrate undergoes rearrangement to an aldehyde under [1,2] hydrogen migration and cleavage of an oxygen-based leaving group. The leaving group is trapped as its formic ester, and the aldehyde is reduced and subsequently esterified to a formate. Whereas the rearrangement to the aldehyde is catalyzed by sulfonic acids, the reduction step requires a unique catalyst system comprising a PdII or Pd0 precursor in loadings as low as 0.75 mol % and α,α′-bis(di-tert-butylphosphino)-o-xylene as ligand. The reduction step makes use of formic acid as an easy-to-handle transfer reductant. The substrate scope of the transformation encompasses both aromatic and aliphatic substrates and a variety of leaving groups.
Iron-Catalyzed Methylation Using the Borrowing Hydrogen Approach
Polidano, Kurt,Allen, Benjamin D. W.,Williams, Jonathan M. J.,Morrill, Louis C.
, p. 6440 - 6445 (2018/07/25)
A general iron-catalyzed methylation has been developed using methanol as a C1 building block. This borrowing hydrogen approach employs a Kn?lker-type (cyclopentadienone)iron carbonyl complex as catalyst (2 mol %) and exhibits a broad reaction scope. A variety of ketones, indoles, oxindoles, amines, and sulfonamides undergo mono- or dimethylation in excellent isolated yields (>60 examples, 79% average yield).
Mechanistic Insight into Additions of Allylic Grignard Reagents to Carbonyl Compounds
Bartolo, Nicole D.,Woerpel
, p. 10197 - 10206 (2018/09/06)
Allylic Grignard reagents exhibit high reactivity and low selectivity in additions to carbonyl compounds. Additions of allylic Grignard reagents to carbonyl compounds were investigated using prenylmagnesium chloride as a mechanistic probe. When the carbonyl group is relatively unhindered, the addition proceeds through a six-membered transition state with allylic transposition. This process generally occurs with no diastereoselectivity because the reaction rates approach the diffusion limit. With hindered ketones, however, this pathway is disfavored, and the addition proceeds through a transition state resembling that of other Grignard reagents.
Additions of Organomagnesium Halides to α-Alkoxy Ketones: Revision of the Chelation-Control Model
Read, Jacquelyne A.,Yang, Yingying,Woerpel
supporting information, p. 3346 - 3349 (2017/07/13)
The chelation-control model explains the high diastereoselectivity obtained in additions of organometallic nucleophiles to α-alkoxy ketones but fails for reactions of allylmagnesium halides. Low diastereoselectivity in ethereal solvents results from no chelation-induced rate acceleration. Additions of allylmagnesium bromide to carbonyl compounds are diastereoselective using CH2Cl2 as the solvent even though rate acceleration is still absent. Stereoselectivity likely arises from the predominance of the chelated form in solution. Therefore, a revised chelation-control model is proposed.
Sodium iodide-catalyzed direct α-alkoxylation of ketones with alcohols via oxidation of α-iodo ketone intermediates
Zhu, Cuiju,Zhang, Yuanfei,Zhao, Huaiqing,Huang, Shijun,Zhang, Min,Su, Weiping
, p. 331 - 338 (2015/02/19)
The direct α-alkoxylation of ketones with alcohols via a sodium iodide-catalyzed oxidative cross-coupling has been developed. This protocol enables a range of alkyl aryl ketones to cross couple with an array of alcohols in synthetically useful yields. The mechanistic studies provided solid evidence supporting that an α-iodo ketone was a key reaction intermediate, being converted into an α-alkoxylated ketone via further oxidation to a hypervalent iodine species rather than a common nucleophilic substitution, and was generated from the ketone starting material via a radical intermediate. These new mechanism insights should have an effect on the design of iodide-catalyzed oxidative cross-coupling reactions between nucleophiles.
Oxidative iodination of carbonyl compounds using ammonium iodide and oxone
Marri, Mahender Reddy,MacHarla, Arun Kumar,Peraka, Swamy,Nama, Narender
supporting information; experimental part, p. 6554 - 6559 (2012/01/02)
A simple, efficient, mild, and regioselective method for oxyiodination of carbonyl compounds has been reported by using NH4I as the source of iodine and Oxone as an oxidant. Various carbonyl compounds such as aralkyl ketones, aliphatic ketones (acyclic and cyclic), and β-keto esters proceeded to the respective α-monoiodinated products in moderate to excellent yields. Unsymmetrical aliphatic ketones reacted smoothly yielding a mixture of 1-iodo and 3-iodo ketones with the predominant formation of 1-iodoproduct.
Product studies and laser flash photolysis on alkyl radicals containing two different β-leaving groups are consonant with the formation of an olefin cation radical
Bales,Horner,Huang,Newcomb,Crich,Greenberg
, p. 3623 - 3629 (2007/10/03)
1-Bromo-2-methoxy-1-phenylpropan-2-yl (3) and 2-methoxy-1-phenyl-1-diphenylphosphatopropan-2-yl (4) were generated under continual photolysis from the respective PTOC precursors in a mixture of acetonitrile and methanol. The radicals undergo heterolytic fragmentation of the substituent in the β-position to generate the olefin cation radical (5). Z-2-Methoxy-1-phenylpropene (15) is the major product formed in the presence of 1,4-cyclohexadiene, and is believed to result from hydrogen atom transfer to the oxygen of the olefin cation radical, followed by deprotonation. Laser flash photolysis experiments indicate that reaction between 5 and 1,4-cyclohexadiene occurs with a rate constant of ～6 × 105 M-1 s-1. 2,2-Dimethoxy-1-phenylpropane (18) is observed as a minor product. Laser flash photolysis experiments place an upper limit on methanol trapping of 5 at k 3 M-1 s-1 and do not provide any evidence for the formation of reactive intermediates other than 5. The use of two PTOC precursors containing different leaving groups to generate a common olefin cation radical enables one to utilize product analysis to probe for the intermediacy of other reactive intermediates. The ratio of 15:18 is dependent upon hydrogen atom donor concentration, but is independent of the PTOC precursor. These observations are consistent with the proposal that both products result from trapping of 5 that is formed via heterolysis of 3 and 4.
Novel cerium(IV) ammonium nitrate mediated transformation of styrenes to α-methoxy acetophenones
Nair, Vijay,Nair, Latha G.,Panicker, Sreeletha B.,Sheeba,Augustine, Anu
, p. 584 - 585 (2007/10/03)
Styrenes when treated with a methanolic solution of CAN underwent a novel transformation to α-methoxy acetophenones presumably via a radical cation.
Stereoselectivities in AgBF4-catalyzed and photoinduced phenyl- rearrangement of 2-chloropropiophenone
Usui, Satoshi,Matsumoto, Takeshi,Ohkubo, Katsutoshi
, p. 9755 - 9758 (2007/10/03)
(S)-2-Phenylpropionic acid was stereoselectively obtained by the AgBF4- catalyzed phenyl-rearrangement of (S)-2-chloropropiophenone dimethyl acetal, while the photoirradiation of (S)- or (R)-2-chloropropiophenone afforded partially racemized (S)-or (R)-2-phenylpropionic acid, respectively. An intramolecular S(N)2 mechanism is suggested for the former rearrangement. The latter result is indicative of the intervention of an ion or radical intermediate in the photoinduced phenyl-rearrangement.
