Reaction of P(III) chlorides with aldehydes: III. Reaction of primary intermediates with oxidants and chlorinating agents

Primary intermediates of P(III) chlorides reaction with aldehydes have been converted into the corresponding phosphates by treating with oxidants: dimethylsulfoxide and tert-butyl hypochlorite. In reactions of the intermediates with chlorinating agents (PCl₅ and Cl₂) the oxidation products are formed (due to the ligand exchange at quasiphosphonium center) along with the expected P(IV) acid chlorides.     

Improved preparation of β-hydroxy-α-amino acids: direct formation of sulfates by sulfuryl chloride

Two β-(alkyl)-β-hydroxy-α-amino acids [alkyl = Bu^t, BnO–(CH₂)₃–] have been synthesized by a sequence based on Sharpless asymmetric dihydroxylation. The key sulfate intermediates were prepared from enantiomerically enriched diols by direct treatment with sulfuryl chloride. The scope and the appropriate conditions for sulfate formation have also been studied.     

An efficient synthesis of N-arylated, orthogonally protected racemic aspartates

A brief and efficient synthesis of variously N-arylated racemic aspartates has been achieved by two consecutive reactions in one-pot, in which imine or equivalent, formed in situ from various anilines and ethyl glyoxylate, reacted with the Reformatsky reagent, tert-butyl 2-bromozinc acetate. Notably the two esters are orthogonally protected for the convenience of further derivatization.     

Experimental and theoretical studies of a silver complex of O-functionalized N-heterocyclic carbene

Experimental and theoretical studies of a silver complex namely, [1-i-propyl-3-(2-oxo-2-t-butyl ethyl)imidazol-2-ylidene]AgCl (1b), supported over an O-functionalized N-heterocyclic carbene ligand are reported. Specifically, [1-i-propyl-3-(2-oxo-2-t-butyl ethyl)imidazol-2-ylidene]AgCl (1b) was synthesized by reaction of 1-i-propyl-3-(2-oxo-2-t-butyl ethyl)imidazolium chloride 1a with Ag₂O in 42% yield. The 1-i-propyl-3-(2-oxo-2-t-butyl ethyl)imidazolium chloride 1a was synthesized by the alkylation reaction of 1-i-propylimidazole with α-chloropinacolone in 70% yield. The molecular structures of 1a and 1b have been determined by X-ray diffraction. Detailed theoretical investigation has been performed using the density functional theory method with the B3LYP functional. Bonding in 1b has been probed with the help of charge decomposition analysis (CDA), atoms in molecule (AIM) approach as well as natural bond orbital (NBO) methods. The Ag-NHC bond has a dominantly covalent character with NHC acting as an effective σ-donor. The π-back-bonding from the metal to the ligand was found to be negligible.     

Oxidation and chlorination reactions of perfluoroketene-N,S-acetals

The paper presents the results of the investigation of oxidation and chlorination reactions of perfluoroketene-N,S-acetals. Oxidation reactions of perfluoroketene-N,S-acetals proved to be dependent on the nature of oxidizing agent and led to the formation of corresponding sulfone in the case of m-chloroperbenzoic acid or amides of α-H-perfluoroalkane carboxylic acids in the case of tert-butyl hydroperoxide or hydrogen peroxide. Reaction of 1-tert-butylsulfanyl-2,3,3,4,4,4-hexafluoro-1-[N-methyl,N-((S)-α-methylbenzyl)amino]-but-1-ene with sulfuryl chloride demonstrated the chlorination of perfluoroketene-N,S-acetals as a new approach in the synthesis of chiral α-chloro perfluoroalkane carboxylic acid amides.     

Highly efficient copper/palladium-catalyzed tandem Ullman reaction/arylation of azoles via C-H activation: synthesis of benzofuranyl and indolyl azoles from 2-(gem-dibromovinyl)phenols(anilines) with azoles

In this paper, a novel and highly efficient copper/palladium-catalyzed tandem intramolecular Ullman-type C-O(N) coupling reaction of 2-(gem-dibromovinyl)phenols(anilines) followed by an intermolecular arylation of azoles through C-H activation has been developed. In the presence of CuBr with Pd(PPh₃)₂Cl₂ used as co-catalyst, and LiO^tBu as a base, the one-pot reactions of 2-(gem-dibromovinyl)phenols and 2-(gem-dibromovinyl)anilines with a variety of azoles, including oxazoles, imidazoles, thiazoles, and oxadiazoles underwent smoothly in toluene at 100 °C to generate the corresponding biheteroaryl products in high yields. A tentative mechanism of copper/palladium-catalyzed tandem reaction was described.     

Homolytic reductive alkylation of methylvinyl ketone with ethers by Ti(III) decomposition of t-butyl hydroperoxide

Reductive alkylatin of methylvinylketone has been accomplished by hydrogen abstraction from cyclic ethers with the redox couple: t-butyl hydroperoxide-titanous chloride. A redox radical mechanism is proposed and the selectivity of the hydrogen abstraction by t-butoxy radicals and reduction of α-ketoalkyl radical by titanous ions is discussed.     

Reaction of tert-butyl hypochlorite with carbonium ion from styrene epoxide in an acidic alcoholic solution

The kinetic regularities of the change in the concentration of tert-butyl hypochlorite in the presence of the binary system (BS) styrene epoxide??p-toluenesulfonic acid in a tert-butanol solution were studied using iodometry and HPLC and compared with the data obtained earlier for hydroperoxide decomposition. The expressions for the rates of transformation of Bu^tOCl, epoxide, and ROOH in the BS through the reactant concentrations are of the same type (the first order for the acid and the zero order for epoxide, Bu^tOCl, and ROOH) and indicate that the reactions are related to epoxide heterolysis. Dioxygen ceases ROOH decomposition in the BS but exerts no effect on the decrease in the concentration of Bu^tOCl, which efficiently inhibits the O₂ uptake in the BS and almost an order of magnitude retards the accumulation of benzaldehyde (the product of styrene epoxide oxidation) with a low (up to 15%) decrease in the heterolysis rate. The inhibition effect is due to the heterolytic interaction of Bu^tOCl with the carbocation formed by the cleavage of the three-membered ring of protonated styrene epoxide. The introduction of Bu^tOCl in the BS decreases the stationary concentration of the carbocation and, as a consequence, the stationary concentration of phenylcarbene responsible for O₂ uptake.     

The use of organotin compounds in the thermal stabilization of poly(vinyl chloride). Part III. Reactions of dialkyltin mercaptides,thioglycollates, and carboxylates with chlorohydrocarbons

Reactions of dialkyltin mercaptides, thioglycollates, and carboxylates with the poly-(vinyl chloride) model compounds tert-butyl chloride and 3-chlorobut-1-ene have been studied. At 180° the tertiary and allylic chlorine atoms in the model compounds undergo exchange reactions with the SR, SCH₂COOR, and OCOR groups attached to tin. In the case of 3-chlorobut-1-ene, the exchange reactions are accompanied by allylic rearrangements. The relevance of these results to the stabilization of poly(vinyl chloride) is discussed.     

Thermodynamic and lfer studies for the oxidation of anilines by the periodate ion

The various thermodynamic parameters for the periodate oxidation of six anilines, viz. aniline, p-chloroaniline, p-ethoxyaniline, o- and p-methoxyanilines and p-methylaniline have been reported and discussed. The validity of the isokinetic relationship and various linear free energy relationships (LFERs) have been tested and discussed. An attempt has been made to correlate these findings with the mechanism operative in these reactions.     

Diphospholyl and triphospholyl zirconium π-complexes: Ziegler–Natta oligomerization catalysts and reactive intermediates in P–C cage formation by hydrolysis

2,4,5-Tri(t-butyl)-1,3-diphospholyl sodium salt (2a) and 3,5-di(t-butyl)-1,2,4-triphospholyl sodium salt (3a) react with ZrCl₄ and CpZrCl₃ to form (η⁵-2,4,5-tri(t-butyl)-1,3-diphospholyl)ZrCl₃ (4), Cp(η⁵-2,4,5-tri(t-butyl)-1,3-diphospholyl)ZrCl₂ (5), and Cp(η⁵-3,5-di(t-butyl)-1,2,4-triphospholyl)ZrCl₂ (6) in the complete absence of water, respectively. Surprisingly, bent sandwich complex 6 exhibits the NMR spectroscopic characteristics of a hindered ring ligand rotation but the cyclopentadienyl ligand of 5 rotates freely in the NMR time scale in spite of the superior space demand of its 2,4,5-tri(t-butyl)-1,3-diphospholyl ligand. This contradiction is discussed on the basis of an attractive interligand P–C interaction between homo- and heterocyclic π-ligands, which is stronger for 6. Water even in trace amounts present in the reaction mixture changes the course of the reactions completely. No zirconium π-complexes are accessible this way, but only oligo- or polycyclic organophosphorus compounds. Compound 3a and ZrCl₄ form the asymmetric tricyclic P₆(t-BuC)₄H₂ isomer 8 with two PC double bonds as a dimer of 1,2,4-triphosphol. It is accompanied by small amounts of HCl addition product 9, where one of the PC double bonds is eliminated. Compound 8 contains six, and 9 eight stereogenic centers, but both form one pair of enantiomers each only. A single stereoisomer of P₆(t-BuC)₄H₂ cage 10 is formed if (1-trimethylstannyl)-3,5-di(t-butyl)-1,2,4-triphosphol 3b is used as the P₃(t-BuC)₂ source in combination with Cp¹ZrCl₃ in the presence of trace amounts of water. Compound 10 is a meso-compound, which is composed by dimerization of either two homochiral units of (R)-3,5-di(t-butyl)-1,2,4-triphosphol 3cR or by two units of its S-enantiomer 3cS. No trace of cyclic addition products has been identified, which would represent the heterochiral combination of enantiomers 3cR + 3cS. P₂- and P₃-zirconocene dichloride derivatives 5 and 6 have been tested as Ziegler–Natta alkene oligomerization catalysts. Both are catalytically active with 1-hexene as the substrate, but cannot compete with the activity of the phosphorus-free original catalyst Cp₂ZrCl₂.     

Chemical standards in ion mobility spectrometry

Positive ion mobility spectra for three compounds (2,4-dimethylpyridine (2,4-DMP, commonly called 2,4-lutidine), dimethyl methylphosphonate (DMMP) and 2,6-di-t-butyl pyridine (2,6-DtBP)) have been studied in air at ambient pressure over the temperature range 37-250 °C with (H₂O)_nH⁺ as the reactant ion. All three compounds yield a protonated molecule but only 2,4-dimethylpyridine and dimethyl methylphosphonate produced proton-bound dimers. The reduced mobilities (K₀) of protonated molecules for 2,4-dimethylpyridine and DMMP increase significantly with increasing temperature over the whole temperature range indicating changes in ion composition or interactions; however, K₀ for the protonated molecule of 2,6-di-t-butyl pyridine was almost invariant with temperature. The K₀ values for the proton-bound dimers of 2,4-dimethylpyridine and DMMP also showed little dependence on temperature, but could be obtained only over an experimentally smaller and lower temperature range and at elevated concentrations. Chemical standards will be helpful as mobility spectra from laboratories worldwide are compared with increased precision and 2,6-di-t-butyl pyridine may be a suitable compound for use in standardizing reduced mobilities. The effect of thermal expansion of the drift tube length on the calculation of reduced mobilities is emphasized.     

The oxidative-rearrangement of 1-amino-2-indolinones. A synthesis of 2-substituted-3(2H)-cinnolinones

Several 2-substituted-3(2H)-cinnolinones have been synthesized by a ring expansion of the respective 1-substituted-2-indolinones via an oxidative-rearrangement with t-butyl hypochlorite.     

RuCl3-TBHP mediated allylic oxidation of Δ lanosterol derivatives

A variety of Δ⁸⁽⁹⁾-lanosterol derivatives were converted into 7,11-dienones using t-butyl hydroperoxide in the presence of ruthenium chloride (RuCl₃) in good yields.     

Unprecedented carbocyclization of 1,6-allenynes on addition of organoboronic acids under Pd-catalysis

In contrast to the ene behavior of allenes in Pauson-Khand reactions and other cyclization reactions, 1,6-allenynes undergo unprecedented carbocyclization followed by regioselective addition of organoboronic acids in the presence of Pd(OAc)₂ and tri-t-butyl phosphine under mild reaction conditions.     

Microwave-assisted synthesis and reverse saturable absorption of phthalocyanines and porphyrins

Soluble phthalocyanines, including tetrakis(2,9,16,23-cumylphenoxy) copper phthalocyanines (CuPc(β-CP)₄), tetrakis(1,8,15,22-cumylphenoxy) copper phthalocyanines (CuPc(α-CP)₄) as well as tetrakis(2,9,16,23-tert-butyl) copper phthalocyanines (CuPc(β-t-butyl)₄), and porphyrins (5,10,15,20-tetrakis(4-tert-butylphenyl)porphyrins; M(TBP), M=H₂, Zn, Cu, Mg, InCl, AlCl) have been quickly synthesized by microwave irradiation. Furthermore, their reverse saturable absorption have also been investigated by dissolving them in solvent or incorporating them in polymer-silica hybrid material with a sol-gel process with polyvinyl butyral and tetraethyl orthosilicate as precursors. A new method for the preparation process of phthalocyanines and porphyrins in the solids has been successfully used.     

Studies on ferrocene derivatives. Part 12. Substituent effects for the disproportionation, synproportionation and ligand exchange reactions of t-butylferrocenes

Summary The disproportionations and synproportionations of t-butylferrocenes and the ligand exchanges between the ferrocenes and benzene have been studied. The steric effects of the t-butyl groups were found to significantly affect the ratio of the products obtained. In these reactions, aluminium chloride attacks and abstracts the cyclopentadienyl ring. As a result, the ferrocene molecule decomposes into two fragments. The aluminium chloride selectively attacks the least sterically hindered cyclopentadienyl ring. The steric effect for a cyclopentadienyl ring bearing two t-butyl groups is substantial and inhibits attack by aluminium chloride. The product therefore contains the cyclopentadienyl ring which has the higher steric hindrance (i.e. the 1,3-di-substituted cyclopentadienyl ring). T. Hayashi, Y. Okada and T. Yamashita, Nippon Kagaku Kaishi, 900 (1995) (Part 11 of this series).     

Unexpected conversion of alkyl azides to alkyl iodides and of aryl azides to N-tert-butyl anilines

In the presence of tert-butyl iodide, alkyl azides are converted into the corresponding iodides at room temperature, whereas, N-t-Bu anilines are obtained from aryl azides under the same experimental conditions. A mechanism is proposed to explain this unusual reactivity.     

The sensitized photodehydrochlorination of poly(vinyl chloride)—II. Model compound studies

p-Cresol, a model compound for an additive shown previously to be a potent photosensitizer of dehydrochlorination in poly(vinyl chloride) PVC, has been shown to sensitize dehydrochlorination in t-butyl chloride, a model for PVC. A quantitative study of the effect of chlorinated alkanes upon the fluorescence of p-cresol in solution reveals that quenching is due to charge transfer interactions, the halogenated compound acting as electron acceptor. Since the mono-halo compound t-butyl chloride does not quench p-cresol fluorescence, it was concluded that the photosensitization occurs via the triplet state of the p-cresol, and this view was confirmed by addition of triplet quenchers. A mechanism for the reaction is proposed, initial exciplex formation being followed by electron transfer.     

A novel synthetic method of dihydro-4-pyrone derivatives and its application to the syntheses of ar-atlantone and (±)-ar-turmerone

Reaction of 1,3-dihalo-3-methy]-2-butanone with t-butyl acetoacetate (NaH) gave t-butyl 3,4-dihydro-2,2,6-trimethyl-4-oxo-2H-pyran-5-carboxylate via the Favorskii-type rearrangement. Michael addition of 4-methylphenyllithium (CuI) followed by ring cleavage with Me₃ SiCl-NaI in DMF or PrCN afforded ar-atlantone as well as (±)-ar-turmerone selectively.