Elimination Of Acetic Acid Research Articles

Transformation of steroidal 5α,8α-peroxides to the 14-membered ring containing 5,10;8,9-diseco-steroid derivatives

Thermal decomposition of steroidal 5α,8α-peroxides (such as 1) resulted in bisfragmentation of the C(5)-C(10) and C(8)-C(9) bonds, and elimination of acetic acid, to produce a new type of bicyclic compounds, namely 5,10;8,9-diseco-steroid derivatives (such as 2). some chemical transformations of product 2 are described.

Reactions at the rhodium vertex of isomeric closo-bis(triphenylphosphine)hydridorhodacarboranes, alkenyl acetate cleavage and subsequent reactions

The isomeric hydridophosphinorhodacarboranerhodium(III) clusters, [ closo-3,3-(PPh 3) 2-3-H-3,1,2-RhC 2B 9H 11] ( 1a); [ closo-2,2-(PPh 3) 2-2-H-2,1,7-RhC 2B 9H 11] ( 1b); and [ closo-2,2-(PPh 3) 2-2-H-2,1,12-RhC 2B 9H 11] ( 1c) react with isopropenyl acetate and vinyl acetate under mild conditions to give ester CO bond scission, expulsion of alkene, and formation of bidentate or monodentate acetate complexes of the form (PPh 3)(η 2-CH 3COO)RhC 2B 9H 11 or (PPh 3) 2(η 1-CH 3COO)RhC 2B 9H 11. These acetate complexes react readily with hydrogen to regenerate the parent compounds. A very stable alkyl complex chelated through the carbonyl oxygen could be isolated from the reaction of 1b with vinyl acetate at lower temperatures, whereas the reaction of 1a with either isopropenyl acetate or vinyl acetate at higher temperatures led to the formation of an ortho-metallated complex whose crystal structure is reported. When allyl acetate was employed as substrate, complexes of the form (PPh 3)(η 3-C 3H 5)RhC 2B 9H 11 resulted with concomitant elimination of acetic acid. The relevance of the novel compounds reported here to the catalytic hydrogenolysis of alkenyl acetates using 1a–1c as catalyst precursors is discussed.

Sesbanimide A and related tumor inhibitors from Sesbania drummondii: Structure and chemistry

Extracts of Sesbania drummondii seed have yielded three new glutarimide tumor inhibitors which are markedly active in the PS leukemia ( in vivo) system and in the KB cell culture system. Structures of sesbanimide A, sesbanimide B, sesbanimide C, acetylation products of the sesbanimides and five compounds obtained by hydrogenating sesbanimide A under mild conditions have now been established using high-field 1H NMR, 13C NMR and mass spectral correlations. Treatment of sesbanimide A diacetate with sodium bicarbonate in aqueous methanol gives rapid elimination of acetic acid and two subsequent products derived via solvolysis of the glutarimide ring.

Unimolecular gas-phase thermolysis of ethyl acetate

The unimolecular gas-phase thermolysis of ethyl acetate has been investigated by the Flash-Vacuum-Thermolysis/Field-Ionization Mass Spectrometry (FVT/FI-MS) method in combination with Collision Activation (CA) mass spectrometry at 1253K. Two predominant reactions are observed: elimination of ethylene affording acetic acid, the latter to some extent consecutively yielding ketene, and intramolecular oxygen to oxygen ethyl group migration. Additionally minor amounts of acetaldehyde is formed. The mechanistic aspects are discussed based on 18O and 18O/ 13C labelling.

A new synthesis of α-methylene carbonyl compounds

α-Methylene carbonyl compounds are regioselectively prepared by the reaction of α-nitroketones or α-nitroesters with 37% formaldehyde in the presence of a catalytic amount of weak bases followed by acetylation, denitration with Bu 3SnH, and elimination of acetic acid.

Intramolecular Stereospecific Pummerer Reactions of Aryl (Substitutedmethyl) Sulfoxides Bearing Electron-withdrawing Groups with Acetic Anhydride

Abstract The Pummerer reaction of optically active cyanomethyl aryl sulfoxides with acetic anhydride gave the corresponding α-acetoxy sulfides which were induced with a partial asymmetry nearly 30% at α-carbon, while the 18O-label of the original sulfoxides was retained in more than 85% in the resulting ester, the Pummerer reaction product. Kinetic experiments with cyanomethyl (p-substituted phenyl) sulfoxides and α,α-dideuterated cyanomethyl p-tolyl sulfoxide in the reaction with acetic anhydride containing a small amount of acetic acid revealed that the rates were correlated with Hammett σ-values and ρ-value of −0.70 was obtained, while the kinetic isotope effect was practically nil, i.e., kH⁄kD=1.01. These observations indicate clearly that the rearrangement is intramolecular and proceeds via forming a very intimate ion-pair and the rate-determining step is believed to be the S–O bond cleavage after the initial reversible acylation and deprotonation. Elimination of acetic acid proceeds through the Elcb type process. The uneven distribution of 18O in the two oxygens of the resulted ester, i.e., ether and carbonyl oxygens, suggests the recombination of the α-sulfenyl carbonium ion and acetate ion to be very rapid. The Pummerer reaction of optically active N,N-dimethyl-p-tolyl-sulfinylacetamide with excess acetic anhydride also gave the corresponding α-acetoxy sulfide in optically active form. In the presence of dicyclohexylcarbodiimide (DCC), the Pummerer reaction was found to be highly stereoselective affording the corresponding α-acetoxy sulfide with 65%e.e. Other optically active α-carbonyl-substituted alkyl sulfoxides, i.e., ethyl p-tolylsulfinylacetate and ω-(p-tolylsulfinyl)acetophenone also gave the corresponding highly optically active Pummerer rearrangement products in the treatment with acetic anhydride/DCC system. The Pummerer reaction of the 18O-labeled sulfoxides with acetic anhydride/DCC system gave the corresponding α-acetoxy sulfides which retained much of the original 18O-labels of the sulfoxides. These observations reveal clearly that in the Pummerer reaction of these compounds the acetoxyl migration is intramolecular and takes place through intimate ion-pairs.

Synthesis with sulfones (n oXXX) : Stereoselective synthesis of arenesulfonyl-1,3-dienes.

Basic treatment of allylic 1,1-disulfones gives 1-arenesulfonyl 1,3-dienes, Condensation of aldehydes with lithiated allylic sulfones and in situ acetylation of the alkoride thus formed followed by basic elimination of acetic acid leads to EE 2-arenesulfonyl 1,3-dienes. Good to very good stereoselectivity can be achieved.

Intermolecular Stereoselective Pummerer Reactions of 4-(p-Chlorophenyl)thiane 1-Oxides and trans-1-Thiadecalin 1-Oxides and 2-Thiadecalin 2-Oxides with Acetic Anhydride

Abstract The Pummerer reactions of conformationally fixed 4-(p-chlorophenyl)thiane 1-oxides and trans-1-thiadecalin 1-oxides and trans-2-thiadecalin 2-oxides with acetic anhydride are either stereoselective or stereospecific, both in the absence and in the presence of a scavenger of acetic acid formed, such as dicyclohexylcarbodiimide (DCC) or 2,6-lutidine. However, the 18O-tracer experiments with the 18O-labeled sulfoxide revealed the reaction to be an intermolecular rearrangement, while the kinetic experiment with α-deuterated 4-(p-chlorophenyl)thiane 1-oxides gave sizable values of kinetic isotope effect, i.e., 2.8 for the cis isomer and 3.4 for the trans isomer. In the reaction of 4-arylthiane 1-oxides with acetic anhydride, the thermodynamically controlled product is axial 2-acetoxy-4-(p-chlorophenyl)thiane while the kinetically controlled product is the equatorial isomer which is formed in the presence of the acid scavenger, DCC. In the Pummerer reaction of the thiadecalins S-oxides the equatorial α-acetoxy sulfides are the preferential products, however, the isomer preference is more pronounced in the reaction with DCC. These observations, along with other pertinent data seem to suggest that the rate-determining step in the Pummerer reaction of these simple heterocyclic sulfoxides is E2 elimination of acetic acid from the acetoxysulfonium intermediates.

Thermolytic reactions of esters. Part XIII The effect of electron‐attracting α‐substituents in alkyl acetates

Abstractα‐Alkylation of esters, e.g. AcO‐iPr → AcO‐tBu, results in a large rate increase for β‐elimination of acetic acid, indicating that in the transition state Cα is positively charged. Replacement of α‐H by electron‐attracting groups Z, such as COOMe, also enhances the rate of formation of alkene. Neither differences in product stability nor steric acceleration appear to play a significant role. A major factor is dipolar destabilization of starting compounds containing two electronegative groups, such as AcOCMe2Z compared with AcO‐tBu. The free energies of the transition states are found to parallel those of the fully ionized species, AcO(‐) + R(+).At elevated temperatures, esters such as AcOCMe(CN)Ph will give rise to O‐C bond homolysis rather than to molecular elimination of acetic acid.

A mass spectral investigation of water and acetic acid elimination from 1‐ and 2‐indan derivatives

AbstractWater and acetic acid eliminations from 1‐ and 2‐indan derivatives have been investigated. Deuterium labeling, high resolution peak matching and the metastable peak analysis capabilities of a high resolution triple analyzer (E B E) mass spectrometer were employed to examine the eliminations. These experiments showed that water was lost from 1‐indanol via 1,2 and 1,3 processes. These results contrast with those obtained for 1‐tetralol, which specifically eliminates water in a 1,4 process involving the benzylic hydrogens. Water elimination from 2‐indanol is preceded by a slow hydroxyl‐benzylic hydrogen exchange and proceeds specifically 1,2. Water losses from both 1‐ and 2‐indanol are characterized by large kinetic energy releases. Acetic acid elimination is shown to occur specifically 1,3 from 1‐acetoxyindan and 1,2 from 2‐acetoxyindan.

A comparison between the stereoselective thermal-induced and ionization-induced elimination of acetic acid from 2-butyl acetate

A comparison between the stereoselective thermal-induced and ionization-induced elimination of acetic acid from 2-butyl acetate

PARTICIPANT OF SEROTONIN TURNOVER RATE IN THE BRAIN ON BARBITAL WITHDRAWAL CONVULSION

The correlation between the development of barbital (B)-withdrawal signs and alterations in the metabolism of brain 5-hydroxy-tryptamine (5-HT) was studied. Barbital (B)-dependent rats were prepared by the B-Admixed Food method (DAF method). The B-dependent rats were grouped according to the following 5 states: G-I. B-dependent state; G-II. B-withdrawan state; G-III, cross-administration of nitrazepam (NZP) following B-withdrawal; G-IV, cross-administration of chlorpromazine (CPZ) following B-withdrawal; and G-V, cross-administration of Phenytoin following B-withdrawal. The controls were comprised of naive rats (G-VI) and naive rats dosed in the same manner as the dependent rats. The brain 5-HT synthesis rate and the brain 5-hydraxyindole acetic acid (5-HIAA) elimination were measured at 44 to 48 hr after B-withdrawal in all groups (when withdrawal convulsion was still persisting in the B-withdrawn rats of the G-II group). The brain 5-HT synthesis rate was elevated significantly (P<0.001) in the rats with persistent B-withdrawal convulsion (G-II) as compared with that in the B-dependent rats (G-I). Cross-administration of nitrazepam caused the elevation of 5-HT synthesis rate with B-withdrawal to be inhibited to the dependent level in parallel with the inhibition of B-withdrawal signs. On the other hand, CPZ and Phenytoin, which inhibit B-withdrawal convulsion slightly, failed to recover completely the 5-HT turnover rate during B-withdrawal. From these results, it is obvious that the elevation of the brain 5-HT synthesis rate with B-withdrawal plays an important role in eliciting B-withdrawal convulsion.

Participant of serotonin turnover rate in the brain on barbital withdrawal convulsion.

The correlation between the development of barbital (B)-withdrawal signs and alterations in the metabolism of brain 5-hydroxytryptamine (5-HT) was studied. Barbital (B)-dependent rats were prepared by the B-Admixed Food method (DAF method). The B-dependent rats were grouped according to the following 5 states: G-I, B-dependent state; G-II, B-withdrawn state; G-III, cross-administration of nitrazepam (NZP) following B-withdrawal; G-IV, cross-administration of chlorpromazine (CPZ) following B-withdrawal; and G-V, cross-administration of phenytoin following B-withdrawal. The controls were comprised of naive rats (G-VI) and naive rats dosed in the same manner as the dependent rats. The brain 5-HT synthesis rate and the brain 5-hydraxyindole acetic acid (5-HIAA) elimination were measured at 44 to 48 hr after B-withdrawal in all groups (when withdrawal convulsion was still persisting in the B-withdrawn rats of the G-II group). The brain 5-HT synthesis rate was elevated significantly (P less than 0.001) in the rats with persistent B-withdrawal convulsion (G-II) as compared with that in the B-dependent rats (G-I). Cross-administration of nitrazepam caused the elevation of 5-HT synthesis rate with B-withdrawal to be inhibited to the dependent level in parallel with the inhibition of B-withdrawal signs. On the other hand, CPZ and phenytoin, which inhibit B-withdrawal convulsion slightly, failed to recover completely the 5-HT turnover rate during B-withdrawal. From these results, it is obvious that the elevation of the brain 5-HT synthesis rate with B-withdrawal plays an important role in eliciting B-withdrawal convulsion.

Synthesis of the natural enantiomers of irones from (+)-citronellal

Some irone isomers with the natural chirality have been synthesised from (+)-citronellal (7). (+)-Methyl citronellate (21) obtained from compound (7) was methylated stepwise to give methyl 2,2,3,7-tetramethyloct-6-enoate (23). After hydrolysis of the ester (23), the resulting acid was converted into the corresponding acyl chloride, which was then cyclised by means of tin(IV) chloride to give 2,2,3-trimethyl-6-(1-chloro-1-methylethyl)cyclohexanone (24). The cyclohexanone (24) was dehydrochlorinated, reduced, acetylated, and then ozonised to give 2-acetoxy-3,3,4-trimethylcyclohexanone (27). The Wittig reaction of the ketone (27) with methoxymethylenetriphenylphosphorane followed by hydrolysis and elimination of acetic acid provided 3,3,4-trimethylcyclohexene-1-carbaldehyde (28). The vinyl ether of an allylic alcohol obtained by reduction of the aldehyde (28) was thermolysed to give the key intermediate, 1-(2,2,3-trimethyl-6-methylenecyclohexyl)acetaldehyde (13), stereoselectively. Elongation of the side-chain in (13) afforded (+)-trans-γ-irone (32a) as the major product. Treatment of the irone (32a) with phosphoric acid yielded (–)-trans-α-irone (2).

The mechanism of the gas-phase pyrolysis of esters. Part 13. The very strong activating effects of β-trialkylmetal groups

The rates of gas-phase pyrolysis of β-substituted ethyl acetates AcOCH2CH2X where X = SiMe3, SiEt3, GeEt3, and SiMe2Ph, and of 1-aryl-2-trimethylsilylethyl acetates have each been measured over a minimum of 50 °C, between 282 and 397 °C; the rates of pyrolysis of 2-aryldimethylsilylethyl acetates have been measured at 396.9 and 378.2 °C. The β-organometallic substituents are not themselves eliminated (except at considerably higher temperatures) but strongly accelerate the normal elimination of acetic acid, the relative rates per β-hydrogen at 327 °C for X being: H, 1.0; SiMe3, 125; SiEt3, 179; GeEt3, 108; SiMe2Ph, 144. These groups appear to activate by a combination of increasing the acidity of the β-hydrogen via stabilisation of the forming β-carbanion through (p→d)π bonding, stabilisation of the incipient α-carbocation by C–X hyperconjugation, and steric acceleration. The effect of substituents in the aryl ring of 1-aryl-2-trimethylsilylethyl acetates gave an excellent correlation with σ+ values with ρ–0.52 at 327 °C. The lower ρ-factor for this reaction compared to that for 1-arylethyl acetates (–0.66) is consistent with either conjugative stabilisation of the α-carbocation or increased β-hydrogen acidity. Substituents in the aryl ring of 2-aryldimethylsilylethyl acetates gave a very small positive ρ-factor indicating that overall their effect on β-hydrogen acidity is larger than that on the forming carbocation. The product of pyrolysis of AcO·CH2·CH2·GeEt3viz. CH2CHGeEt3 underwent increasingly rapid elimination of successive moieties, believed to be ethylene, in a reaction of stoicheiometry 4.0, which did not occur with the silicon analogue.

Stereoselective synthesis of 2-alkylidene-3,4-dihydro-3-oxo-2h-1,4-benzothiazines

Metallation of 4-methyl-3,4-dihydro-3-oxo--2H-1,4-benzothiazine with LDA and subsequent reaction with aldehydes leads to diastereomeric aldols 4 and 5. Acetylation followed by acetic acid elimination of the aldols provides a stereoselective and high yield route to 2-alkylidene-3,4-dihydro-3-oxo-2H-1,4-benzothiazines.

ChemInform Abstract: PREPARATION OF (E)‐1,3,5‐HEXATRIENE AND (3E,5E)‐1,3,5,7‐OCTATETRAENE BY THE PALLADIUM CATALYZED ELIMINATION OF ACETIC ACID FROM ALLYLIC ACETATES

AbstractDie Pd(II)‐ katalysierte Essigsäure‐Eliminierung aus den Estern (I) oder (III) führt zu dem Trien (II), und zwar entsteht (II) aus (I) streng stereoselektiv, aus (III) als E/Z‐Gemisch (80:20, Gesamtausb.

Preparation of (E)-1,3,5-Hexatriene and (3E, 5E)-1,3,5,7-Octatetraene by the Palladium Catalyzed Elimination of Acetic Acid from Allylic Acetates

Abstract Palladium complex-catalyzed elimination of acetic acid from (2E,4E)-2,4-hexadienyl acetate and (2E, 4E, 6E)-2,4,6-octatrienyl acetate afforded, respectively, the title conjugated polyenes stereoselectively.

Evaluation of kinetic parameters of the thermal decomposition of polyethylene-vinyl acetate graft copolymers

The thermal decomposition of the polyethylene-vinyl acetate graft copolymers was studied by thermogravimetry (nonisothermal conditions, constant heating rate of 4‡/min). Between 275 and 350‡ the thermal decomposition is due to the splitting of the acetoxy groups of the grafted chains and the elimination of acetic acid. The reaction order, activation energy and frequency factor were computed by means of the Coats-Redfern and Fuoss methods. The activation energy and frequency factor valuesobtained with the two methods agree well and they do not depend on the grafted vinyl acetate content (2.6–17.6%).

Phosphine substitution and phosphine induced reductive elimination reactions: synthesis of zerovalent ruthenium fluorophosphine complexes from hydrido(acetato)tris(triphenylphosphine)ruthenium(II)

Substitution of PPh 3 from the bidentate acetatohydridoruthenium(II) complex RuH(CH 3OCO)(PPh 3) 3 with various ligands, L, leads to unidentate acetatohydrido compounds with replacement of one, two or all PPh 3 ligands depending on L (L = t-BuNC, PF 2NMe 2, P(OCH 2) 3CMe, P(OMe) 3, dppe). On the other hand acetic acid elimination from RuH(CH 3OCO)(PPh 3) 3 occurs with fluorophosphines to yield zerovalent ruthenium complexes RuL′ 5 (L′ = PF 2NMe 2, PF 2NC 4H 8), RuL 4(PPh 3) (L′ = PF 3) and RuL 3(PPh 3) 2 (L′ = PF 3).