Detailed mechanism generation. 2. Aldehydes, ketones, and olefins

Generalized reaction classes for the consumption and decomposition of aldehydes, ketones, and olefins are described. These classes are important for generating not only reactions for the consumption of the branching agents of low-temperature hydrocarbon combustion but also reactions of the oxidation of alkenes and the decomposition of cyclic ethers. These reaction classes have been extrapolated from specific reactions of existing validated mechanisms. The reaction patterns making up the class were derived by identifying the reactive center of the specific reactions and the important surrounding functional groups. The rates used currently are definitely "first guesses" based on these specific reactions. The reaction classes in this paper supplement the reaction classes derived from accepted reaction types in the previous paper in this series. The purpose of this paper is to outline a complete (with very few exceptions) set of reaction classes which describe the C(5) and C(6) products of the low-temperature and cyclic ether path in the heptane and isooctane mechanisms.     

Catalytic asymmetric Mannich reactions of glycine derivatives with imines. A new approach to optically active alpha,beta-diamino acid derivatives

Imines of glycine alkyl esters react with imines in a diastereo- and highly enantioselective Mannich reaction in the presence of chiral copper(I) complexes as the catalyst to give optically active alpha,beta-diamino acid derivatives. A series of imines of glycine esters derived from glycine and aromatic carbonyl compounds has been screened as substrates for the Mannich reaction with different imines in the presence of various combinations of metal salts and chiral ligands. The benzophenone imine of glycine esters was found to react with N-protected imines in a diastereoselective fashion giving functionalized alpha,beta-diamino acid esters with excellent enantioselectivities. The most effective chiral catalysts are chiral copper(I) complexes having phosphino-oxazoline (P,N)-ligands, and among these ligands, those derived from (1R,2S)-dihydroxy-1,2,3,4-tetrahydronaphthalene gave the best results. The scope of this new catalytic asymmetric reaction of the benzophenone imine glycine esters is demonstrated for the reaction with different N-protected-C-aryl and C-alkyl imines giving the Mannich adducts with excellent optical purity. Furthermore, the synthetic aspects of the reaction are presented by converting the Mannich adducts into alpha,beta-diamino acid derivatives. The relative and absolute configuration of the Mannich adduct have been determined and based on the stereochemical outcome of the reaction a tetrahedral chiral-copper(I)-imino glycine alkyl ester intermediate is proposed. In this intermediate the Re-face of the benzophenone imine glycine ester is shielded by the chiral ligand leaving the Si-face available for approach of the Si-face of the imine. A series of semiempirical calculations has been performed to support the structure of the tetrahedral chiral-copper(I) complex and to account for the influence of the substituents in the chiral phosphino-oxazoline ligands.     

Studies on the syntheses of benzoquinone ansamycin antibiotics. Syntheses of the C5-C15 subunits of macbecin I, geldanamycin, and herbimycin A

[reaction: see text] A general and convergent route to the C(5)-C(15) subunits of the benzoquinone ansamycin antibiotics macbecin I, geldanamycin, and herbimycin A is described. Each subunit is prepared by the stepwise coupling of differentially functionalized aldehydes with a pentenyl dianion equivalent derived from diastereoselective pentynylation and regioselective reductive coupling.     

Addition reactions of iodomethyllithium to imines. A direct and efficient synthesis of aziridines and enantiopure amino aziridines

An efficient and general synthesis of aziridines by the reaction of imines derived from p-toluenesulfonamides with in situ generated iodomethyllithium, with a simple and rapid experimental protocol, is reported for the first time. The reaction with the chiral aldimine derived from phenylalaninal allowed access to (2R,1'S)-2-(1'-aminoalkyl)aziridine with very high diastereoselectivity, in enantiopure form. A mechanism to explain this novel reaction is proposed.     

Re-examination of the anodic oxidation of N,N-dimethylaniline, using parametric method 3

A semi-empirical calculation (PM3) was applied to elucidate the anodic oxidation mechanism of N,N-dimethylaniline (DMA) and the dimerization of a cation radical (A) derived from DMA was ruled out. The heat of reaction value of the dimerization of A was 42.43 kcal/mol. We propose the following. Cation radical A reacts with DMA to generate another cation radical (D). This reaction was exothermic and the heat of reaction value and the activation energy were -0.35 kcal/mol and 1.31 kcal/mol, respectively. Deprotonation of D by DMA gives neutral radical (E), which is oxidized to TMB by A. All these reactions were exothermic.     

Vibrational levels of methanol calculated by the reaction path version of MULTIMODE, using an ab initio, full-dimensional potential

An accurate potential energy surface has been determined for methanol from ab initio potential data at the CCSD(T) level of theory with an aug-cc-pVTZ basis. The resulting potential function is valid over all twelve vibrational degrees of freedom for all near-equilibrium and torsional configurations. A torsional reaction path has been derived for this potential, from which the low-lying vibrational levels of methanol have been calculated by the reaction path version of MULTIMODE. Comparisons with experiment and other calculations are made.     

Photoreactions of quinine in aqueous citric acid solution. part 2, some end-products

A novel spiro-compound derived from 2',4'-b1s-(1,3-dicarboxy-2-hydroxyprop-2-y1) -1',4'-dihydroquinine has been identified as a major end-product of the irradiation of quinine in aqueous citric acid solution. 7'-(1,3-Dicarboxy-2-hydroxyprop-2-yl)deoxyquinine and products arising from the cleavage of quinine at C-9 were also detected in the reaction mixture.     

Aroylation of n-alkylmethanimines. A synthesis of novel substituted 2-aza-buta-1,3-dienes.

The aroylation of carbanions derived from N-benzyl-diphenylmethanimine and N-(diphenylmethyl )-arylmethanimines yields highly substituted 2-aza-buta- 1,3-dienes in which the imino group is conjugated with an enol ester. A similar reaction with N-(diphenylmethyl)-diphenylmethylmethanimine qives the expected iminoketone.     

Formation,structure, and elasticity of loosely crosslinked epoxy-amine networks. I. Statistics of formation

Using the theory of branching processes based on cascade substitution, relations are derived for structural parameters characterizing network formation from diepoxide, monoepoxide, and diamine for various initial compositions. The different reactivities of the hydrogen atoms of the primary and secondary amino groups (the latter being formed in the reaction) and possibly different reactivities of epoxy groups in diepoxide and monoepoxide are taken into account. Relations are derived for the critical conversion at the gel point and for changes as a function of conversion in the average molecular weight in the pregel stage, changes in the sol and gel contents, effective functionality of the crosslinks, and concentration of elastically active network chains. The derivation includes the trapping factor that appears in the theory of permanent interchain interactions (trapped entanglements) of the Langley type. An analysis of the approximation usually employed in the statistical theory based on network formation from dyads of structural units shows that this approach is quite satisfactory for small differences in the reactivities of epoxy groups in diepoxide and monoepoxide.     

Studies on the synthesis of landomycin A. Synthesis of the originally assigned structure of the aglycone, landomycinone, and revision of structure

The originally proposed structure (2) of landomycinone, the aglycone of landomycin A, has been synthesized and shown to be nonidentical to the naturally derived landomycin A aglycone. The synthesis of 2 features the D?tz benzannulation reaction of chromium carbene 5 and alkyne 6, and the intramolecular Michael-type cyclization reaction of the phenolic naphthoquinone 20. It is proposed that natural landomycinone possesses the alternative structure 3, but attempts to access this structure via the Michael-type cyclization of the isomeric phenolic naphthoquinone 38 have been unsuccessful.     

General strategy for stereoselective synthesis of 1-substituted exo,endo-2,6-diaryl-3,7-dioxabicyclo[3.3.0]octanes: total synthesis of (+/-)-gmelinol

[reaction: see text] A general strategy for stereoselective synthesis of 1-substituted exo,endo-2,6-diaryl-3,7-dioxabicyclo[3.3.0]octanes including (+/-)-gmelinol from (2,3-trans)-(4,5-cis)-alpha-aroylparaconic esters, which are readily obtained from the reaction of vicinal dianions derived from alpha-aroylsuccinic esters with aromatic aldehydes, is described. The synthetic sequence involves alpha-methylation or alpha-hydroxylation, reduction, bislactonization, and reduction followed by furofuran formation.     

A catalytic, highly stereoselective aldehyde olefination reaction

A catalytic aldehyde olefination reaction has been discovered. A Cu(II) complex (5 mol %) derived from a salen-quinine mixed ligand catalyzed the reaction between aldehydes and two molecules of acetyl chloride to produce trans C-C double bonds exclusively. The new catalytic aldehyde alkenation reaction presumably goes through a C-3 acylated β-lactone intermediate that loses one molecule of CO₂.     

Synthetic studies on mitomycins. 2. A synthesis of 9a-hydroxy-5,8-dideoxomitosane skeleton through a novel retroaldol type of ring-opening reaction.

A synthesis of 9a-hydroxy-5,8-dideoxomitosanes was accomplished by the transannular cyclization of hydro-1-benzazocinone intermediates derived from 3-(2,5-dioxo-1-methylcyclopentyl)-6-methyl-p-phenylenediamine derivatives. These mitosanes were led to the 8-membered ring system by an oxidative ring-opening reaction.     

Total synthesis of myxothiazols, novel bis-thiazole beta-methoxyacrylate-based anti-fungal compounds from myxobacteria

Convergent total syntheses of myxothiazols A and Z are described. The syntheses are based on elaboration of the (S)-E,E-diene thioamide 22, conversion of 22 into the bis-thiazole 27 and Wittig reactions between 27c and the aldehyde 30. The substituted beta-methoxyacrylate aldehyde 30 was produced via an Evans asymmetric aldol protocol or via the 2H-pyran-2-one 31. An E-selective Wittig reaction between the ylide derived from the phosphonium salt 27c and the (+)-aldehyde 30 led to (+)-myxothiazol Z (1b), and a corresponding reaction with the (+/-)-acrylamide aldehyde 44 gave (+/-)-myxothiazol A (1a). Complementary studies led to synthesis of the ester 47b, corresponding to myxothiazol R and myxothiazol S.     

Asymmetric PTC C-alkylation catalyzed by chiral derivatives of tartaric acid and aminophenols. Synthesis Of (R)- and (S)-alpha-methyl amino acids

A new type of efficient chiral catalyst has been elaborated for asymmetric C-alkylation of CH acids under PTC conditions. Sodium alkoxides formed from chiral derivatives of tartaric acid and aminophenols (TADDOL's 2a-e and NOBIN's 3a-h) can be used as chiral catalysts in the enantioselective alkylation, as exemplified by the reaction of Schiff's bases 1a-e derived from alanine esters and benzaldehydes with active alkyl halides. Acid-catalyzed hydrolysis of the products formed in the reaction afforded (R)-alpha-methylphenylalanine, (R)-alpha-naphthylmethylalanine, and (R)-alpha-allylalanine in 61-93% yields and with ee 69-93%. The procedure could be successfully scaled up to 6 g of substrate 1b. When (S,S)-TADDOL or (R)-NOBIN are used, the (S)-amino acids are formed. A mechanism rationalizing the observed features of the reaction has been suggested.     

Conjugate addition of (trimethylstannyl)copper reagents to α,β-acetylenic N,N-dimethylamides. Trapping of the intermediates with electrophiles

A study of the reaction of Me₃SnCu·.Me₂S (1) and [Me₃SnCuSPh]Li (2) with α,β - acetylenic N,N-dimethylamides 3 shows (a) that the overall process can be controlled experimentally so as to produce either N,N-dimethyl ($\text{E}$)-(4) or ($\text{Z}$)-3-trimethylstannyl-2-alkenamides (5), (b) that the initially formed intermediate derived from interaction of 2 and 3 is significantly more stable than that obtained by reaction of 2 and α,β-acetylenic esters, and (c) that the intermediate produced by treating 3 with 1 can be trapped with electrophiles other than proton.     

An efficient,one-pot,three-component procedure for the synthesis of chiral spirooxindolopyrrolizidines via catalytic highly enantioselective 1,3-dipolar cycloaddition

The catalytic, highly regio-, diastereo-, and enantioselective synthesis of a small library of chiral spirooxindolopyrrolizidines via a three-component 1,3-dipolar cycloaddition reaction of azomethine ylides, derived from isatin, with electron-deficient dipolarophiles, 3-(2-alkenoyl)-1,3-oxazolidin-2-ones, is described. A chiral copper(II) complex of cyclohexane-1,2-bis(arylmethyleneamine) catalyzed this process at room temperature. The reaction mechanism is discussed on the basis of the assignment of the absolute configuration of the cycloadducts.     

Trimethylsilylated N-alkyl-substituted carbamates: II. Alcoholysis of trimethylsilyl N,N-dimethylcarbamate

The reaction of trimethylsilyl N,N-dimethylcarbamate with the sterically hindered alcohol 2-methylbutan-2-ol has been studied kinetically. The reaction shows autocatalytic character, and an equation has been derived which satisfactorily describes the kinetic behaviour. A mechanism is suggested for the reaction.     

Polyanhydrides. XI. Poly(Ester-anhydride)s Derived from 4-Hydroxybenzoic Acid,Vanillic Acid,and Aliphatic Dicarboxylic Acids

ABSTRACT

Poly(ester-anhydride)s, PEA's, built up by 50 mol% ester and 50 mol% anhydride groups were prepared by polycondensation of 0,0′-bistrimethylsilyl 4-hydroxybenzoic acid and various α,ω- alkane-dicarbonylchlorides. The polycondensations were conducted either in bulk or in 1-chloronaphthalene. High yields (up to 94%) were obtained under both reaction conditions, but the higher inherent viscosities resulted from polycondensations in 1- chloronaphthalene. IR- and ¹³C NMR spectroscopy revealed that reaction temperatures above 200°C cause side reactions such as transacylation and transesterification. Analogous series of polycondensations were conducted with 0,0′-bistrimethylsilyl vanillic acid. The resulting PEA's were amorphous, whereas the PEA's derived from 4-hydroxybenzoic acid are semicrystalline.     

Model for a three-center decomposition reaction. I. Perfluorodiazirine

A semiempirical approach has been used to evaluate rate parameters for a three-center decomposition reaction from the point of view of transition state theory, with perfluorodiazirine serving as the prototype molecule. Several activated complex models are considered in which the reaction coordinate is chosen as the ? NCN bending mode. The constraints imposed include the principle of concerted bond-order conservation in passing from the initial to the final state, and use is made of empirical bond order–bond length and bond order–force constant relationships. The geometric configuration of the transition state sought is one which conforms with the lowest energy path and is also consistent with the observed entropy of activation. The potential energy of activation is taken as the optimum difference in binding energies (based on the INDO method) between the transition and initial states, and the critical energy is obtained by applying a correction for the zero-point energy difference, derived from normal coordinate analysis. Satisfactory agreement is found in the case of the activated complex model for which the total bond order is conserved and bonds undergoing rupture are assigned a fractional bond order (FBO) of 2/3, derived from the postulate (FBO) = α/β whe re α(=2) is the number of bonds breaking, and β(=3) is the number of bonds undergoing change in the ring opening.