Corey-Chaykovsky Reaction Research Articles

( Z)-Selective Wittig and Corey–Chaykovsky reactions of propargyl ylides using trialkylgallium bases

Trialkylgalliums deprotonated propargylphosphonium salts and propargylsulfonium salts to form propargyl ylides. The resulted organogallium intermediates underwent the Wittig reaction and the Corey–Chaykovsky reaction with aldehydes giving ( Z)-enynes and ( Z)-epoxides predominantly. The use of an appropriate trialkylgallium is essential for the stereoselectivity.

A study of influence of temperature and N, N-acyl protected keto ylides structure on their predominant transformations

The effect of temperature and keto ylides structure on preference of their intramolecular cyclization leading to N-containing heterocyclic compounds or linear products formation has been investigated at the B3LYP/6-31G(d,p) level of theory. It has been determined that the thermodynamic advantage of the cyclization reactions of ylides increases with temperature, while Gibbs free energies of linear products formation reactions depend insignificantly on temperature. The Wittig and the Corey–Chaykovsky reactions are least probable in the case of the sulfonium and ammonium ylides considered. However, for phosphonium ylides the Wittig reaction must be considerably preferable in comparison with other routes, while behavior of the arsonium ylides is predicted to be more complex. Research of S-ylides transformations shows that formation of methylthio-substituted heterocycles with five-, six- or seven- membered rings is possible from a thermodynamic standpoint, while conversion of the corresponding ylide to a four-membered heterocycle is disadvantageous. Presence of a methyl substituent and its position in the ylide carbon chain depends ambiguously on the behavior of sulfur keto ylides.

D-Glucosamine trimethylene dithioacetal derivatives: formation of six- and seven-membered ring amino carbasugars. Synthesis of (–)-calystegine B3,

By virtue of carefully chosen protecting groups, d-glucosamine trimethylene dithioacetal derivatives were successfully oxidized to the corresponding 6-aldehydes. This methodology reverses the donor and acceptor position on a normal open chain sugar and changes the relative position of the N-substituent. From the 6-aldehydes, heptose epoxide derivatives were prepared by a Corey-Chaykovsky reaction, and cyclized by the Corey-Seebach method. Depending on the designed protecting groups, the orthogonally protected six- and seven-membered ring amino carbasugars can be produced selectively and efficiently. (-)-Calystegine B(3) was synthesized from one of those products with high yield. This is the first anionic cyclization pathway to calystegine type structures.

Quantum chemical study of the effect of N,N-acyl group nature on the structure and Gibbs free energy of the sulfur ketoylides and products of their transformations

With the purpose to study the effect of the nature of the imido-group of N,N-acyl-protected β-methyl-substituted keto-stabilized sulfonium ylides on the formation of methylthiopyrrolisinediones by cyclization, the structure features of these ylides are investigated by ab initio methods. The imido-group nature is shown to insignificantly affect in most cases the structure and the relative free energy of conformers of the ketoylides in question and the products of a cyclization reaction with their participation. The energy difference between the anti-peri-planar and syn-clinal orientation of nitrogen atoms in the imido-group and ylide carbon atom is negligible. The latter orientation is necessary for the reaction of intramolecular cyclization to proceed because in this case carbon atoms between which the bond forms are drawn together. The structure of cyclic pentanomial N,N-acyl group slightly affects the calculated values of Gibbs free energy of sulfur ketoylide reactions, and a temperature increase promotes the intramolecualr cyclization reactions. Wittig and Corey-Chaykovsky reactions typical of ylides are the least thermodynamically favorable for the sulfonium ketoylides under study.

Study of mechanisms of sulfonium keto ylides intramolecular cyclization

Mechanisms of monomolecular cyclization of N-maleyl protected keto stabilized sulfur ylides via three reaction pathways were investigated at the B3LYP/6-31G(d,p) level of theory. Structures and Gibbs free energies of intermediates and transition states of the reactions show that the Corey–Chaykovsky reaction occurs without trans-betaine formation and is least probable among those considered. Although methylthio pyrrolisinedione formation is thermodynamically most favorable, it has been found that an activation barrier of intramolecular 1,4-methyl shift, which is proposed to be a rate-limiting step in the reaction mentioned, is considerably high. However, the Wittig reaction, possessing lowest activation energy of the rate-limiting step, is thermodynamically disadvantageous. The presence of an alkyl substituent at the β-position of ylide and temperature influence only a new carbon–carbon bond formation at first stage of ylide cyclization.

Efficient microwave-assisted synthesis of 1-(1 H-indol-1-yl)-2-phenyl-3-(1 H-1,2,4-triazol-1-yl)propan-2-ols as antifungal agents

New conazole antifungals, in the series of triazole alcohols 23a– d and 24a– e incorporating an indole moiety substituted at 5-position by halogens, a cyano or 4-methoxyphenyl group, have been synthesized by ring opening of corresponding oxiranes 15 and 16. These dihalogeno intermediates and their congeneers could be prepared in high yields by Corey–Chaykovsky reaction under microwave irradiation.

A study of the dependence of substituted N, N-acyl defended keto stabilized sulfur ylides structure on their transformations by means of quantum chemistry

The effect of substituents and the nature of imide groups on the behavior of N, N-acyl defended carbonyl stabilized sulfur ylides was investigated. The comparison of Gibbs free energies of reactions obtained at the B3LYP/6-31G(d,p) level shows that the Wittig and the Corey–Chaykovsky reactions are least profitable for all considered ylides. It is found that the thermodynamic preference of methylthio pyrrolisindiones formation grows with temperature while formation of linear products does not depend on temperature. The presence of substituent in the β-position and the nature of the cyclic imide group have considerable influence on the preferable transformations of ylides.

Quantum chemical research of structures and some transformations of phthalimido-substituted keto-stabilized sulfur ylides

The behavior and structure of molecules of phthalimido-substituted keto-stabilized sulfur ylides have been investigated by means of ab initio (RHF/6-31G(d,p), MP2(fc)/6-31G(d,p), MP2/6-31G(d,p), MP2(fc)/6-31+G(d,p), MP2/6-31+G(d,p) and B3LYP/6-31G(d,p)) methods of quantum chemistry. The influence of the structure of ylides on their reactivity has been researched on the basis of a novel reaction of intramolecular cyclization. The results of the analysis of conformers indicate that the presence of the alkyl substituent at the β-position leads to a diminution of the distance between interacting functional groups. The comparison of the found values of Gibbs free energies in some possible reactions of ylides calculated at various temperatures leads to the conclusion that the higher temperature, the greater the thermodynamic preference of the cyclization reaction. The influence of the temperature on the formation of linear by-products is significantly lower. From the point of view of thermodynamic preference, it is improbable for the Wittig and Corey–Chaykovsky reactions to be the most characteristic for ylides.

Revisiting the Corey–Chaykovsky reaction: the solvent effect and the formation of β-hydroxy methylthioethers

The classical Corey–Chaykovsky (CC) reaction of ketones in ethereal solvents (i.e., THF or Et 2O) resulted in the production of a significant amount of β-hydroxy methylthioether 2 along with normal epoxide product 1 . Some interesting and synthetically useful transformations of the CC reaction product of cyclopropyl ketones were also described.

The Isopropylsulfinyl Group: A Useful Chiral Controller for the Asymmetric Aziridination of Sulfinylimines and the Organocatalytic Allylation of Hydrazones

[reaction: see text] A comparative study shows that the isopropylsulfinyl group for which an enantiodivergent and highly diastereoselective approach is reported behaves better than the tert-butylsulfinyl and p-tolylsulfinyl groups, both in terms of reactivity and stereoselectivity in the Corey-Chaykovsky reaction of chiral sulfinylimines and the organocatalytic allylation of acyl hydrazones.

Synthesis of Novel Reactive Polymers Having Oxirane Structure in the Main Chain by Polycondensation of Bis(sulfonium ylide) with Dialdehyde

Poly(phenylenevinylene oxide)s (PPVOs) having oxirane groups in the main chain were prepared by the Corey–Chaykovsky reaction between bis(sulfonium ylide)s and dialdehydes. The sulfonium ylide formed in situ from m-xylylenebis(dimethylsulfonium perchlorate) by the use of lithium diisopropylamide (LDA) as a base was reacted with terephthalaldehyde to afford m,p-PPVO with Mn=3600. Oxirane groups in PPVO were successfully reacted with various reagents such as acetic acid, lithium aluminum hydride and n-octylamine to give the corresponding ring-opening products. The properties of the ring-opened polymers reflected the structure of the reagents used for the polymer reactions. These results showed that PPVOs are novel reactive polymers whose properties can easily be adjusted by polymer reactions.

2,3] Sigmatropic Rearrangement of Unstable Sulfur Ylides from Allyl Sulfonium Salts. Comparative Study of Electrochemical Reduction with the Base Method and Mechanism Elucidation by the MO Method

Abstract The cathodic reduction of sulfonium salts in acetonirile under the presence and absence of benzaldehyde were carried out and compared with the results of the base method. Under the presence of benzaldehyde, the electrochemical reduction gave epoxides as a result of a Corey–Chaykovsky reaction confirming ylide formation. The electrochemical reduction of sulfonium salt without benzaldehyde yields the same [2,3] sigmatropic rearrangement product as those obtained by the base method, in high yield. The reaction mechanism was studied by semi-emprical MO methods.

Corey—Chaykovsky Reaction of Chiral Sulfinyl Imines: A Convenient Procedure for the Formation of Chiral Aziridines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Generation of Sulfur Ylides from Sulfonium Salts and Their Reactions. Comparative Study of Electrochemical Reduction with the Base Method and Mechanism Elucidation by the MO Method

Abstract The cathodic reduction of sulfonium salts in acetonitrile in the presence and absence of benzaldehyde was carried out. Results were compared with results of the base method. In the presence of benzaldehyde, the electrochemical reduction gave epoxides as a result of the Corey–Chaykovsky reaction, thus confirming ylide formation. The electrochemical reduction of sulfonium salts without benzaldehyde yielded rearrangement products in high yield. On the contrary, upon base treatment of sulfonium salts without benzaldehyde, symmetrical epoxides derived from the benzyl group of the sulfonium salt are obtained as main products as a result of the auto oxidation of the sulfur ylide. The reaction mechanisms were elucidated based on the results obtained by a semi-empirical molecular orbital method.

“Instant Methylide” Modification of the Corey—Chaykovsky Epoxide Synthesis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

“Instant Methylide” Modification of the Corey–Chaykovsky Epoxide Synthesis

We report that Me3S(O)+I− (1) and Me3S+I− (2) form stable, dry mixtures with KOt-Bu and NaH, respectively, which remain stable upon prolonged storage (>1 year). The corresponding methylides (Me2SO=CH2 and Me2S=CH2) are generated upon addition of DMSO or DMSO/THF solutions of carbonyl compounds, cleanly affording epoxides via the Corey–Chaykovsky reaction in good yields and short reaction times (as short as 20 min when 1–2 mmol of various ketones and aldehydes were treated with a mixture of 1 and KOt-Bu at 50–60°C).

Corey-Chaykovsky Reaction of Chiral Sulfinyl Imines: A Convenient Procedure for the Formation of Chiral Aziridines

The reaction of dimethylsulfonium methylide with a range of aromatic, heterocyclic and aliphatic tert-butylsulfinyl imines­ is presented. Aziridines were formed in 63-84% yield and 77-95% diastereomeric excess.

New Heteroorganic Betaines Containing the (+)E15—C—E14—X(‐) and (+)E15—C—E14(‐) Structural Fragments (E15: P, As; E14: Si, Ge, Sn; X: C, S, O, NR)

AbstractFor Abstract see ChemInform Abstract in Full Text.

New heteroorganic betaines containing the (+)E15-C-E14-X(-) and (+)E15-C-E14(-) structural fragments (E15 = P, As; E14 = Si, Ge, Sn; X = C, S, O, Nr)

The review surveys the data on the reactions of phosphorus and arsenic ylides with compounds containing E=X bonds (E = C, Si, Ge, or Sn; X = C or S), cyclic oligomers (R2ES)n (n = 2 or 3), and heavier analogs of carbenes. These reactions give rise to two new classes of heteroorganic betaines containing the (+)E15—C—E14—X(–) (I) and (+)E15—C—E14(–) (II) (E15 = P or As; E14 = Si, Ge, or Sn; X = C or S) structural fragments. Procedures for the synthesis of these compounds, their reactivities, the X-ray diffraction structures, and the electronic structures established by high-level quantum-chemical calculations are considered in detail. The carbon analogs of betaines of type I, viz., compounds bearing the (+)P—C—C—X(–) fragment (III), are also discussed. The latter were long considered as possible intermediates in the reactions of compounds containing the polar C=X bond (X = C, O, S, NR, etc.) with phosphorus ylides (classical Wittig and Corey—Chaykovsky reactions and related processes).

Heteroorganic betaines. 8.* Synthesis and structures of silicon- and germanium-containing organoarsenic betaines R13As+-CR2R3-EMe2-S- (E = Si,Ge)

The reactions of ylides R13As=CHR2 with hexamethyl-2,4,6-trisila- and hexamethyl-2,4,6-trigermatrithiacyclohexanes afforded betaines R13As+—CHR2—SiMe2—S– (2) (R1 = Et; R2 = Ph (a), Me3Si (b); R1 = R2 = Ph (c)) and Et3As+—CH(SiMe3)—GeMe2—S– (3), respectively. Betaines 2a,b and 3 were characterized by multinuclear NMR spectroscopy. According to the X-ray diffraction data, in the crystals the As+—C—E—S– main chain (E = Si or Ge) of molecules 2a,b and 3 adopts a twisted cis conformation due to strong intramolecular Coulomb interactions between the anionic and cationic centers. The equilibrium geometries of isolated molecules 2a and 3, which were calculated within the framework of the density functional theory (the PBE functional, the TZ2P basis set), are in qualitative agreement with the X-ray data. In solutions, betaines 2a (in the absence of Li salts) and 2c (in the presence of LiBr) selectively decomposed according to the Corey—Chaykovsky reaction, which was accompanied by elimination of R3As and, probably, the intermediate formation of silathiirane. The subsequent transformation of the latter afforded 2,2,4,4-tetramethyl-5-phenyl-2,4-disila-1,3-dithiolane.