Dialkyl Acetals Research Articles

Protected syn-Aldol Compounds from Direct, Catalytic, and Enantioselective Reactions of N-Acyl-1,3-oxazinane-2-thiones with Aromatic Acetals.

A direct and asymmetric syn-aldol reaction of N-acyl-1,3-oxazinane-2-thiones with dialkyl acetals from aromatic acetals in the presence of 2-5 mol % [DTBM-SEGPHOS]NiCl2, TMSOTf, and lutidine has been developed. It has been established that the oxazinanethione heterocycle, used for the first time as a scaffold in asymmetric carbon-carbon bond-forming reactions, can be smoothly removed to give access to a variety of enantiomerically pure compounds with high synthetic value.

Ni/Photoredox-Catalyzed C(sp3)-C(sp3) Coupling between Aziridines and Acetals as Alcohol-Derived Alkyl Radical Precursors.

Aziridines are readily available C(sp3) precursors that afford valuable β-functionalized amines upon ring opening. In this article, we report a Ni/photoredox methodology for C(sp3)-C(sp3) cross-coupling between aziridines and methyl/1°/2° aliphatic alcohols activated as benzaldehyde dialkyl acetals. Orthogonal activation modes of each alkyl coupling partner facilitate cross-selectivity in the C(sp3)-C(sp3) bond-forming reaction: the benzaldehyde dialkyl acetal is activated via hydrogen atom abstraction and β-scission via a bromine radical (generated in situ from single-electron oxidation of bromide), whereas the aziridine is activated at the Ni center via reduction. We demonstrate that an Ni(II) azametallacycle, conventionally proposed in aziridine cross-coupling, is not an intermediate in the productive cross-coupling. Rather, stoichiometric organometallic and linear free energy relationship studies indicate that aziridine activation proceeds via Ni(I) oxidative addition, a previously unexplored elementary step.

Conversion of levulinic acid to levulinate ester biofuels by heterogeneous catalysts in the presence of acetals and ketals

The esterification of levulinic acid under acidic conditions to produce levulinate esters is of current significant interest due to the potential of these compounds as fuels and fuel additives. While a number of bespoke heterogeneous catalysts have been reported to be effective for this transformation, the use of widely available commercial catalysts has generally proved to be ineffective, with only low conversions to ester products being achieved. Herein, we report a novel strategy for the efficient synthesis of levulinate esters from levulinic acid in the presence of trialkyl orthoformates or dialkyl acetals and ketals catalyzed by commercial catalysts, such as ZSM-5 and Amberlyst-15. These reactions proceed under mild conditions and in short reaction times to selectively produce high yields of levulinate esters.

Direct anti Glycolate Aldol Reaction of Protected Chiral N‐Hydroxyacetyl Thiazolidinethiones with Acetals Catalyzed by a Nickel(II) Complex

The direct and stereocontrolled addition of (S)‐4‐isopropyl‐N‐(2‐pivaloyloxyacetyl)‐1,3‐thiazolidine‐2‐thione to dialkyl acetals of aromatic and α,β‐unsaturated aldehydes catalyzed by 2.5–5 mol‐% of a nickel(II) complex permits the synthesis of diastereomerically pure and fully protected anti aldol adducts in good to high yields. The catalytic species is formed in situ from commercially available and easy to handle (Me3P)2NiCl2, which makes this reaction a direct, catalytic, and experimentally simple approach to the asymmetric anti glycolate aldol reaction.

N-Alkylation of N-H Compounds in N,N-Dimethylformamide Dialkyl Acetal

<i>N</i>-Alkylation of N-H Compounds in <i>N</i>,<i>N</i>-Dimethylformamide Dialkyl Acetal

Highly selective synthesis under benign reaction conditions of furfural dialkyl acetal using SnCl2 as a recyclable catalyst

A new and mild route of furfural acetalization with various alkyl alcohols catalyzed by cheap and simple SnCl2 has been developed.

A Linear Trinuclear Oxidodiperoxido‐molybdenum(VI) Complex with Single Triazole Bridges: Catalytic Activity in Epoxidation, Alcoholysis, and Acetalization Reactions

AbstractThe complex (Htrz)2[Mo3O6(O2)4(trz)2]⋅H2O (1), isolated from the reaction of MoO3 with H2O2 in the presence of 1,2,4‐triazole (trz), displays singular structural features such as double bridges comprising one oxido and one triazole ligand, and peripheral oxidodiperoxido‐molybdenum(VI) units. A comparative study was performed regarding the catalytic activity and stability of complex 1 and the hybrid material [MoO3(trz)0.5] (2) for the epoxidation of cis‐cyclooctene (Cy8), the alcoholysis of epoxides, and the acetalization of benzaldehyde (PhCHO). Methanol or ethanol were used as solvents and reagents for the latter two reactions. For the substrates Cy8, styrene oxide, and PhCHO, the corresponding epoxide, β‐alkoxy alcohol, and dialkyl acetal were obtained with 100 % selectivity at very high conversions. In general, 1 performed better than 2 for the different catalytic reactions. Under certain oxidant/co‐solvent conditions used for Cy8 epoxidation, 1 was converted to 2 during the reaction.

Stereoselective and Catalytic Synthesis of anti-β-Alkoxy-α-azido Carboxylic Derivatives.

Direct addition of a chiral N-azidoacetyl thiazolidinethione to a variety of dialkyl acetals catalyzed by a commercially available and structurally simple nickel(II) complex gives access in good yields and a highly stereocontrolled manner to anti-β-alkoxy-α-azido carboxylic derivatives which, in turn, can be easily converted into a wide array of enantiomerically pure compounds.

A simple, one-pot oxidative esterification of aryl aldehydes through dialkyl acetal using hydrogen peroxide

A simple and an efficient one-pot procedure has been developed to synthesize various aryl carboxylic esters directly from aryl aldehydes using hydrogen peroxide without any catalyst. The reaction proceeds smoothly at room temperature. A preliminary investigation suggests the formation of dialkyl acetal as an intermediate during the reaction sequence.

Atom-economical synthesis of 3,3,3-trifluoropropanal dialkyl acetals through Pd/C catalyzed acetalization of 3,3,3-trifluoropropene

A facile procedure for one-step synthesis of 3,3,3-trifluoropropanal dialkyl acetals from readily available 3,3,3-trifluoropene has been developed. Atom-economical characteristics of this method are beneficial to industrial applications.

The use of dialkyl acetals in the N-alkylation of 8-oxoadenosine and guanosine. Mechanistic studies and rate determination

The use of seven N,N-dimethylformamide dialkyl acetals (methyl-, ethyl-, benzyl-, n-propyl-, n-butyl-, t-butyl, and neopentyl-) was explored for the exocyclic amine protection and subsequent N-alkylation of 8-oxoadenosine and guanosine. Reactions occurred in good to modest yields (50–95%) upon addition of heat (60°C) using DMF as solvent. We determined relative rates of reaction and kinetic experiments resulted in the following order: Me≫Bn≈t-Bu≫Et≈n-Pr≈n-Bu>Me (Np, neopentyl). We found that groups that stabilize a pseudo-carbocation intermediate facilitate the completion of the reaction and lead to different reaction pathways, including elimination of isobutylene and ethylene in some cases.

Hydrogen Bond Organocatalysis of Benzotriazole in Transamidation of Carboxamides with Amines

A new method of transamidation of carboxamides with amines catalyzed by benzotriazole has been developed. INTRODUCTION Amide bonds are ubiquitous in living systems and play a key role in bioorganic and medicinal chemistry. Carboxamide group was found to appear in more than 25% of known drugs. Amide formation is thus one of the most fundamental reactions in organic synthesis. The most common strategy for amide bond formation is the reaction between amines and carboxylic acids in the presence of stoichiometric amounts of activating reagents. For this approach, the first step is the activation of the acid (acid chlorides, acylimidazoles, acylazides, anhydrides, and active esters), followed by aminolysis. Much effort has been made to develop a catalytic direct amidation. Alternatively, transamidation reaction between a carboxamide and an amine is an attractive tool in synthetic organic chemistry. However, uncatalyzed transamidation required in general drastic heating conditions. Different methods utilizing activating reagents or catalysts have been developed with the objective to decrease the reaction temperature. Despite their wide scope, these protocols required at least one of these conditions: (i) energetically favorable systems (ring-opening of four-membered rings; (ii) intramolecular assistance, or both factors); (iii) use of moisture-sensitive and/or activation reagents (up to 2–3 equivalents; borate esters, dialkylformamide dialkyl acetals, AlCl3, AlMe3, HCl). Examples of transamidation from the Stahl's group provided an elegant possibility of preparing amides under mild † This paper is dedicated to Prof. Victor Snieckus on the occasion of his 77 birthday. HETEROCYCLES, Vol. 88, No. 1, 2014 403

Lewis Acid Catalyzed Intramolecular Condensation of Ynol Ether-Acetals. Synthesis of Alkoxycycloalkene Carboxylates

Treatment of ynol ether-tethered dialkyl acetals with catalytic quantities of scandium triflate in CH(3)CN gives rise to five-, six-, and seven-membered alkoxycycloalkene carboxylates in good to excellent yields. Tri- and tetrasubstituted carbocyclic and heterocyclic alkenes may be formed by this method, and the products obtained may serve as useful intermediates for natural product synthesis.

ChemInform Abstract: A Generalized Approach for Iron Catalyzed Chemo‐ and Regioselective Formation of anti‐Markovnikov Acetals from Styrene Derivatives.

AbstractPh‐I(O‐Ac)2 in the presence of catalytic amounts of Fe(BF4)2 and pyridine‐2,6‐dicarboxylic acid efficiently and selectively promotes the transformation of styrenes into anti‐Markovnikov dialkyl acetals under mild conditions.

A generalized approach for iron catalyzed chemo- and regioselective formation of anti-Markovnikov acetals from styrene derivatives

Fe(BF(4))(2)·6H(2)O in the presence of pyridine-2,6-dicarboxylic acid and PhI(OAc)(2) can efficiently catalyze the formation of chemoselective dialkyl acetals from styrene derivatives with anti-Markovnikov regioselectivity in good to high yields under mild and benign reaction conditions.

ChemInform Abstract: Synthesis of Tri‐ or Tetrasubstituted Pyrimidine Derivatives Through the [5 + 1] Annulation of Enamidines with either N,N‐Dimethylformamide Dialkyl Acetals or Orthoesters and Their Application in a Ring Transformation of Pyrimidines to Pyrido[2,3‐d]pyrimidin‐5‐one Derivatives.

The [5+1] annulation of enamidines, which were prepared from functionalized silanes, organolithium compounds and two nitriles, with N,N-dimethylformamide dialkyl acetals as the C1 unit is described, leading to the synthesis of tri- and tetrasubstituted pyrimidine derivatives under catalyst- and solvent-free reaction conditions. Furthermore, the [5+1] annulation of enamidines by using orthoesters as the C1 unit is described, in which catalytic amounts of ZnBr(2) catalyze the annulation to produce polysubstituted pyrimidines under toluene or xylene reflux conditions. Moreover, the combination of a reductive ring-opening reaction with [Mo(CO)(6)] and a subsequent intramolecular cyclization with tBuOK effectively causes a skeletal transformation from the pyrimidines containing an isoxazolyl and an ethoxy substituent to form pyrido[2,3-d]pyrimidin-5-one frameworks in excellent yield.

Synthesis of Tri‐ or Tetrasubstituted Pyrimidine Derivatives through the [5+1] Annulation of Enamidines with either N,N‐Dimethylformamide Dialkyl Acetals or Orthoesters and Their Application in a Ring Transformation of Pyrimidines to Pyrido[2,3‐d]pyrimidin‐5‐one Derivatives

The [5+1] annulation of enamidines, which were prepared from functionalized silanes, organolithium compounds and two nitriles, with N,N-dimethylformamide dialkyl acetals as the C1 unit is described, leading to the synthesis of tri- and tetrasubstituted pyrimidine derivatives under catalyst- and solvent-free reaction conditions. Furthermore, the [5+1] annulation of enamidines by using orthoesters as the C1 unit is described, in which catalytic amounts of ZnBr(2) catalyze the annulation to produce polysubstituted pyrimidines under toluene or xylene reflux conditions. Moreover, the combination of a reductive ring-opening reaction with [Mo(CO)(6)] and a subsequent intramolecular cyclization with tBuOK effectively causes a skeletal transformation from the pyrimidines containing an isoxazolyl and an ethoxy substituent to form pyrido[2,3-d]pyrimidin-5-one frameworks in excellent yield.

Novel Partial Esterification Reaction in Poly(amic acid) and Its Application for Positive-Tone Photosensitive Polyimide Precursor

We found novel quantitative esterification in poly(amic acid) (PAA) by reacting with N,N-dimethylformamide dialkyl acetals (DFAs). Different alkyl ester was obtained by changing the alkyl group in DFAs. The esterification ratio was determined by amount of DFAs. The reaction proceeds under mild condition without any catalysis. It has not been reported such a kind of quantitative partial esterification before. The partial esterification allowed us to control the solubility of PAA to alkaline solutions. The strict solubility rate control to alkaline solution of PAA was quite important for positive tone photosensitive polyimide (posi PSPI). The partial esterification of PAA gave us a way to strict dissolution control. By using it, we could obtain posi PSPI just mixing with diazonaphthoquinone compound.

A Convenient Synthetic Method for Fluorine-Containing 4-Alkoxydihydrobenzo[b][1,4]diazepinols and 3H-Benzo[b][1,4]diazepines by the Reaction of β-Trifluoroacetylketene Acetals with 1,2-Phenylenediamines

β-Trifluoroacetylketene dialkyl acetals (3 and 5) reacted easily with various 1,2-phenylenediamines to give novel 4-alkoxy-2-trifluoromethyl-2,3-dihydro-1H-benzo[b][1,4]diazepinols (6 and 8) in moderate to high yields. Dehydration of 6 and 8 proceeded thermally under reduced pressure to afford the corresponding fluorine-containing 3H-benzo[b][l,4]diazepines (7 and 9).

Stereoselective Addition of Titanium Enolates to Functionalized Acetals: A Novel Approach to the γ-Amino Acid of Bistramides and FR252921

Dialkyl acetals containing other functional groups can participate in stereoselective coupling reactions with chiral titanium enolates. Such an approach provides the protected γ-amino acid present in bistramides and FR252921 in a highly efficient manner.