Dimethyl Acetals Research Articles

ChemInform Abstract: Multifold Bond Cleavage and Formation Between MeOH and Quinoxalines (or Benzothiazoles): Synthesis of Carbaldehyde Dimethyl Acetals.

AbstractK2S2O8‐mediated treatment of various quinoxalines with MeOH allows a convenient, acid‐, aldehyde‐, and transition metal‐free access to carbaldehyde dimethyl acetals of type (III).

Efficient Iron‐Catalyzed Acetal Formation from Styrene Derivatives

All green in one medium: FeSO4⋅7 H2O in combination with pyridine-2-carboxylic acid and H2O2 in methanol can efficiently catalyze the formation of arylaldehyde dimethyl acetals from the corresponding styrene derivatives.

Syntheses of 3,4-Benzotropolones by Ring-Closing Metatheses

Ortho-lithiated styrenes or ortho-lithiated benzaldehyde dimethyl acetals were added to 2,2-dimethoxypent-4-enals 7. The resulting alcohols were carried on to the aromatic dienones 10. These were ring-closed by olefin metathesis. Hydrolysis of the dimethyl ketal moiety and enolization provided the 3,4-benzotropolones 5. Overall, this access comprises 4-6 steps and totaled a 22-81% yield.

Fatty acid composition of porcine cumulus oocyte complexes (COC) during maturation: effect of the lipid modulators trans-10, cis-12 conjugated linoleic acid (t10,c12 CLA) and forskolin

The effect of maturation and of two lipid modulators supplementation along in vitro maturation (IVM) on fatty acid (FA) and dimethylacetal (DMA) composition of porcine cumulus oocyte complexes (COC) were studied. Abattoir-derived immature COC were analyzed for FA and DMA or submitted to IVM as follows: control group; t10,c12 CLA group, t10,c12 CLA supplementation for 44 h; Forskolin group, forskolin supplementation during the initial 2 h; t10,c12 CLA + forskolin group, t10,c12 CLA for 44 h and forskolin for just 2h. Each experimental group had five replicates. FA analysis of oocytes, cumulus cells (CC), follicular fluid, and culture media were performed by gas-liquid chromatography. Oocytes and their CC had different FA composition. Oocytes were richer in saturated FA (SFA) preferentially maintaining their FA profile during maturation. Mature CC had the highest polyunsaturated FA (PUFA) content. Five individual and total SFA, and monounsaturated FA (MUFA), notably oleic acid (c9-18:1), percentages were lower (P ≤ 0.023) in mature than in immature CC. t10,c12 CLA was accumulated by COC from t10,c12 CLA and t10,c12 CLA + forskolin groups, mostly in CC where MUFA and an eicosatrienoic isomer decreased (P ≤ 0.043). Nevertheless, PUFA or FA and DMA total content were not affected. Arachidonic acid was reduced in t10,c12 CLA + forskolin CC and hexadecanal-DMA-16:0 in t10,c12 CLA CC. Forskolin alone increased (P ≤ 0.043) c9-18:1 in oocytes. In conclusion, maturation process clearly changed porcine COC FA and DMA profiles, mostly of CC, also more susceptible to modifications induced by t10,c12 CLA. This possibility of manipulating COC lipid composition during IVM could be used to improve oocyte quality/cryopreservation efficiency.

Heck reaction of ortho-substituted iodobenzenes with α,β-unsaturated nitriles as a key step in the synthesis of tetrahydro-2-benzazepines and hexahydro-3-benzazocines

A novel strategy is reported for the synthesis of tetrahydro-2-benzazepines 2 and hexahydro-3-benzazocines 3 comprising a Heck reaction of ortho-substituted iodobenzenes 6 and 14 with α,β-unsaturated nitriles. Hydrogenation of the resulting α,β-unsaturated nitriles 7, 11, 15, and 16 was followed by reductive cyclization. It was shown that the formation of 2-benzazepines was faster than the formation of 3-benzazocines, which was explained by the higher stability of the aliphatic dimethyl acetals in 17 and 18. The tetrahydro-2-benzazepine 2d with an N-butyl residue reveals very high σ1 affinity with a Ki-value of 2.0 nM.

ChemInform Abstract: Two Pathways in the Reaction of tert‐Butyl 3‐Oxo‐1‐oxa‐8‐azaspiro[4.5]decane‐8‐carboxylate with N,N‐Dimethylformamide Dimethyl Acetal.

AbstractThe title reaction affords a mixture of two regioisomeric condensation products (III)/(IV), which can be easily transformed into isomeric spirocyclic pyrazoles on treatment with hydrazine hydrate.

Multifold Bond Cleavage and Formation between MeOH and Quinoxalines (or Benzothiazoles): Synthesis of Carbaldehyde Dimethyl Acetals

A K(2)S(2)O(8)-mediated direct cross-coupling of quinoxalines (or benzothiazoles) with methanol leading to 2-quinoxalinyl (or 2-benzothiazolyl) carbaldehyde dimethyl acetals has been achieved. 2-Quinoxalinyl carbaldehyde dimethyl acetals were readily converted into 2-quinoxalinyl carbaldehydes in good to excellent yields under acidic conditions. Preliminary mechanistic studies suggest that the reaction proceeds via multifold bond cleavage and formation between methanol and N-heterocycles involving a dioxygen-participated radical process. This method allows for the synthesis of a variety of 2-quinoxalinyl (or 2-benzothiazolyl) carbaldehyde dimethyl acetals directly via cross-coupling of simple N-heterocyclic C-H bond and methanol under aldehyde-, acid-, and transition-metal-free conditions.

From Biomass to Chemicals: Synthesis of Precursors of Biodegradable Surfactants from 5‐Hydroxymethylfurfural

The selective acetalization of 5-hydroxymethylfurfural (HMF) with long-chain alkyl alcohols has been performed to obtain precursors of molecules with surfactant properties. If direct acetalization of HMF with n-octanol is performed in the presence of strong acids (homogeneous and heterogeneous catalysts), an increase in etherification versus acetalization occurs. Beta zeolite catalyzes both reactions. However, if the acidity of a zeolite (Beta) was controlled by partial exchange of H(+) with Na(+), the dioctyl acetal of HMF can be achieved in 95% yield by transacetalization. It is possible to achieve a high yield in a very short reaction time through a two-step one-pot process, which includes the synthesis of the dimethyl acetal of HMF followed by transacetalization with n-octanol. The one-pot process could be extended to other alcohols that contain 6-12 carbon atoms to afford 87-98% yield of the corresponding dialkyl acetal with a selectivity higher than 96%. The optimized catalyst with an adequate Na content (1.5NaBeta) could be recycled without loss of activity or selectivity.

Anodic Cleavage of Several Ketone N-Phenylsemicarbazones into Methyl N-Phenylcarbamate and the Corresponding Dimethyl Acetals

Several ketone N-phenylsemicarbazones were electrooxidized in the presence of potassium iodide and a base using methanol as the solvent to give nearly commensurate amounts of methyl N-phenylcarbamate and the corresponding dimethyl acetals. Continuous evolution of gaseous nitrogen was observed from the anolyte during the electrooxidation. The reactions were carried out under very mild reaction conditions and are presumed to proceed through a four-electron oxidation process, in which the iodide ion plays an important role as an electron carrier.

Oscillibacter ruminantium sp. nov., isolated from the rumen of Korean native cattle

A strictly anaerobic, Gram-negative, non-spore-forming bacterium, designated GH1(T), was isolated from the rumen of Korean native cattle (HanWoo). Cells were straight to slightly curved rods (2.0-4.5 µm long) and were motile by peritrichous flagella. The isolate grew at 30-45 °C (optimum 40 °C), at pH 5.5-6.5 (optimum pH 6.0) and with up to 3.5% (w/v) NaCl. Strain GH1(T) produced acid from d-glucose, d-ribose and d-xylose, with butyric acid being the major end product. The genomic DNA G+C content was 54.6 mol%. Based on comparative 16S rRNA gene sequence analysis, strain GH1(T) was most closely related to Oscillibacter valericigenes Sjm18-20(T) (97.3% 16S rRNA gene sequence similarity). DNA-DNA hybridization between strain GH1(T) and O. valericigenes DSM 18026(T) showed 24% reassociation. The major fatty acids were iso-C13:0 (13.0%), iso-C15:0 (17.6%), anteiso-C15:0 (8.4%) and C14:0 (4.1%), and the cellular fatty acid methyl esters as dimethylacetals (DMAs) were C16:0 DMA (17.8%), iso-C15:0 DMA (15.2%) and C14:0 DMA (4.52%). The cell-wall peptidoglycan of strain GH1(T) contained meso-diaminopimelic acid and the major cell-wall sugar was galactose. Based on 16S rRNA gene sequence similarity, phylogenetic analysis, DNA G+C content, DNA-DNA relatedness and distinct phenotypic characteristics, strain GH1(T) is classified in the genus Oscillibacter as a member of a novel species, for which the name Oscillibacter ruminantium sp. nov. is proposed. The type strain is GH1(T) (=KCTC 15176(T)=NBRC 108824(T)=JCM 18333(T)).

Tandem Semipinacol-Type 1,2-Carbon Migration/Aldol Reaction toward the Construction of [5–6–7] All-Carbon Tricyclic Core of Calyciphylline A-Type Alkaloids

A Lewis acid promoted tandem semipinacol-type 1,2-carbon migration/aldol reaction of trimethylsilane-protected vinylogous α-ketols with aldehyde or dimethyl acetals is reported. This reaction provides a direct and rapid way for the construction of 6-substituted spiro[4.5]decanes which extensively exist in Daphniphyllum alkaloids. By the use of this method, further construction of a [5-6-7] all-carbon tricyclic core of Calyciphylline A-type alkaloids was also completed.

Diastereoselective Additions of Titanium Enolates from N-Glycolyl Thiazolidinethiones to Acetals

The stereochemical outcome of the Lewis acid-mediated glycolate addition of the titanium enolates from protected N-hydroxyacetyl-4-isopropyl-1,3-thiazolidine-2-thiones to dimethyl and dibenzyl acetals depends on the hydroxyl protecting group. Particularly, the pivaloyl protected glycolate derivative provides the reluctant anti adducts in high yields and diastereomeric ratios, which can be isolated and further converted in enantiomerically pure form to β-methoxy or β-benzyloxy α-pivaloyloxy carbonyl fragments in a straightforward manner.

ChemInform Abstract: An Alternative Approach to Direct Aldol Reaction Based on Gold‐Catalyzed Methoxyl Transfer.

A mild and catalyzed alternative to the direct aldol reaction has been developed based on the gold-catalyzed methoxy group transfer from dimethyl acetals to terminal alkynes. Due to the simultaneous activation of the acetals, this aldol approach is only functional for acetals but not aldehydes. A ligand effect from the gold complex has also been observed.

ChemInform Abstract: One‐Step Conversion of Acetophenones to α‐Haloacetophenone Dimethyl Acetals Using DCDMH/DBDMH and Molecular Sieve in Methanol.

Abstract Using DCDMH/DBDMH as N-halo reagent, piperidine as catalyst, and 4-A molecular sieve as water-removing agent, α-haloacetophenone dimethyl acetals were directly obtained from the solvent of methanol. As to the substrates with electron-withdrawing groups, the conversions were 80–100%.

Synthesis of <i>O</i>-Nitrophenylacetaldehyde

O-nitrotoluene is condensed with N, N-dimethylformamide dimethyl acetals in the presence of piperidine and DMF to yield trans-β-dimethylamino-2-nitrostyrene which undergoes hydrolysis in the 18% HCl aqueous solution to obtain o-nitrophenylacetaldehyde with yield of 83% and purity of 98.1% respectively.

LIPID AND FATTY ACID COMPOSITION OF TWO SPECIES OF ABALONE,HALIOTIS DISCUS HANNAIINO ANDHALIOTIS DIVERSICOLORREEVE

Analyses of lipid profile and fatty acid compositions of muscle and viscera of two commercially cultured abalone, namely Haliotis discus hannai Ino and Haliotis diversicolor Reeve, have been carried out. The total lipid levels of the viscera of both abalone were much higher than those of muscle. Phospholipids were the predominant lipid components in muscle, whereas triacylglycerol in viscera. The major fatty acids identified in muscle and viscera were C16:0, C18:0, C20:4n–6, C20:5n–3 and C22:5n–3. Polyunsaturated fatty acids (PUFAs) accounted for over 40% of total fatty acids, and C20:4n–6 and C20:5n–3 were the most abundant PUFAs. Moreover, different fatty acid compositions were found between the muscle and viscera. Compared with muscle, viscera contained higher percentage of 4,8,12-trimethyltridecanoic acid and C18-PUFA, but lower percentage of C22-PUFA and dimethyl acetals. This study would increase awareness of the nutritional value of these two abalone and also contribute some important information to abalone aquaculture. PRACTICAL APPLICATIONS Haliotis discus hannai Ino and Haliotis diversicolor Reeve are the main commercially farmed species of abalone and have become the most important species of molluscan mariculture in China and occupied the important position in terms of commercial value among farmed molluscan products. This study analyzed the lipid profile and fatty acid compositions of muscle and viscera of the above two abalone species. The results would provide some useful nutrition information for the consumption and aquaculture of abalone. Meanwhile, the viscera of abalone are rich in total lipids and polyunsaturated fatty acid, indicating that the viscera would have great potential of exploitation and comprehensive utilization in lipids.

ChemInform Abstract: Method for the Selective Formation of Dimethyl Acetals in the Presence of Hydroxylamine.

AbstractThe target compounds can be prepared in the presence of either stoichiometric or catalytic amounts of hydroxylamine.

An Alternative Approach to Direct Aldol Reaction Based on Gold‐Catalyzed Methoxyl Transfer

AbstractA mild and catalyzed alternative to the direct aldol reaction has been developed based on the gold‐catalyzed methoxy group transfer from dimethyl acetals to terminal alkynes. Due to the simultaneous activation of the acetals, this aldol approach is only functional for acetals but not aldehydes. A ligand effect from the gold complex has also been observed.

Dimethyl acetals, an indirect marker of the endogenous antioxidant plasmalogen level, are reduced in blood lipids of Sudanese pre-eclamptic subjects whose background diet is high in carbohydrate

In Sudanese women with (n = 60) and without (n = 65) pre-eclampsia, circulating lipids, plasma and red cell saturated and monounsaturated fatty (MUFA) acids and dimethyl acetals (DMAs) were investigated. DMAs are an indirect marker of levels of plasmalogens, endogenous antioxidants, which play a critical role in oxidative protection, and cholesterol homeostasis. The pre-eclamptics had higher C18:1n-9 (p < 0.001) and ΣMUFA (p < 0.01) in plasma free fatty acids, C16:1n-7, C18:1n-9, ΣMUFA; 16:0/16:1n-7 (p < 0.01) in erythrocyte choline phosphoglycerides (ePC) and 16:1n-7, 18:1n-7 and 16:0/16:1n-7 (p < 0.01) in erythrocyte ethanolamine phosphoglycerides (ePE). In contrast, the DMAs 18:0, 18:1 and ΣDMAs in ePE, and 16:0, 18:0 and ΣDMAs in ePC were reduced (p < 0.001) in the pre-eclamptic women. This study of pregnant women with high carbohydrate and low fat background diet suggests pre-eclampsia is associated with oxidative stress and enhanced activity of the microsomal enzyme stearyl-CoA desaturase (delta 9 desaturase), as assessed by palmitic/palmitoleic (C16:0/C16:n-1) and stearic/oleic (C18/C18:1n-9) ratios.

One-Step Conversion of Acetophenones to α-Haloacetophenone Dimethyl Acetals Using DCDMH/DBDMH and Molecular Sieve in Methanol

Using DCDMH/DBDMH as N-halo reagent, piperidine as catalyst, and 4-A molecular sieve as water-removing agent, α-haloacetophenone dimethyl acetals were directly obtained from the solvent of methanol. As to the substrates with electron-withdrawing groups, the conversions were 80–100%.