A new method for the preparation of 2-thio substituted furans by methylsulfanylation of gamma-dithiane carbonyl compounds

Several related methods for the preparation of differentially substituted 2-thiofurans are described. The general procedure involves the formation of a thionium ion from a gamma-dithianyl substituted carbonyl compound followed by cyclization of this reactive intermediate onto the tethered carbonyl group. Two methods for thionium ion generation were explored. One of these involved an acid-catalyzed reaction of beta-ketenedithioacetals, prepared from the condensation of 2,2-bis(methylsulfanyl)acetaldehyde with a variety of ketones. Cyclization followed by loss of methane thiol gave 2-thiofurans 17, 18 and 23, 24 in 70-90% yield. Attempts to prepare 5-heteroatom substituted 2-thiofurans from the corresponding beta-ketenedithioacetal amides or esters were unsuccessful, leading to 1,2-thio rearranged products. A more successful route involved the reaction of beta-acetoxy-gamma-thianyl carbonyl compounds with dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF). Treatment of the dithiane with this reagent resulted in the smooth generation of a thionium ion. Cyclization followed by loss of acetic acid afforded thiofurans 17, 18, 23, 47-49, 51, and 61-64 in 40-100% yield. The N-butenyl substituted thioamido furan furnished a rearranged hexahydropyrroloquinolin-2-one in high yield when heated at 110 degrees C.     

DMAP catalyzed reaction of β-ketoesters and dimethyl acetylenedicarboxylate: efficient synthesis of polysubstituted benzenes and biaryls

A DMAP catalyzed tandem addition-cyclization-dehydration sequence involving dimethyl acetylenedicarboxylate and β-ketoesters leading to polysubstituted benzene/biaryl derivatives is presented.     

DABCO-catalyzed reaction of allenic esters and ketones with salicyl N-tosylimines: synthesis of highly functionalized chromenes

[reaction: see text] DABCO-catalyzed reactions of salicyl N-tosylimines with ethyl 2,3-butadienoate and penta-3,4-dien-2-one proceed smoothly at room temperature in dichloromethane to give the corresponding chromenes in good to excellent yields.     

Synthesis of 3,4-dihydro-2H-pyrans by hetero-Diels-Alder reactions of functionalized alpha,beta-unsaturated carbonyl compounds with N-vinyl-2-oxazolidinone

Cycloadditions of 3-aryl-2-benzoyl-2-propenenitriles and 3-phenylsulfonyl-3-buten-2-one to N-vinyl-2-oxazolidinone proceed regio- and diastereoselectively yielding cis and trans diastereoisomers of 4-aryl-3,4-dihydro-2-(2-oxo-3-oxazolidinyl)-2H-pyrans in 37-65% yield. Cycloadducts cis- were the major products. Reaction of 5-arylidene-1,3-dimethylbarbituric acids with dienophile afforded mixtures of 2H-pyrano[2,3-d]pyrimidine-2,4(3H)-diones trans and products resulted from an elimination of 2-oxazolidinone, in 50-52% yield. To confirm the experimental results, semiempirical AM1 and PM3 calculations of frontier orbital energies have been performed.     

A novel bicyclic phosphonium ylide from the reaction of a 1,2-dihydrophosphorin with dimethyl acetylenedicarboxylate.

The reaction of 1,2,5-triphenylphospholium fluorenylide with dimethyl acetylenedicarboxylate gives two 1:1 adducts, one of which is shown by X-ray analysis to have a novel 1-phosphabicyclo[3.2.1]octatriene structure.     

A modified and green methodology for preparation of polysubstituted furans

In this study, we introduced a very simple, one‐pot and green methodology for preparation of polysubstituted furans by reaction of aromatic aldehydes, DMAD, and alkylisocyanides in water and at room temperature. © 2005 Wiley Periodicals, Inc. 16:259–262, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20086     

Unexpected formation of novel pyrrole derivatives by the reaction of thioamide with dimethyl acetylenedicarboxylate

The reaction of thioamides with DMAD gave the pyrrole derivatives in good yield and the thiophene derivatives as a byproduct. These were formed by 1,3-dipolar cycloaddition of themodynamicaly stable azomethine ylide or less stable thiocarbonyl ylide with DMAD, followed by elimination of thioaldehyde or imine derivatives.     

Product structure in the reaction of dimethyl acetylenedicarboxylate with 2-furyl-1,2,3,4-tetrahydroquinolines

Dimethyl acetylenedicarboxylate reacts with 4-substituted and 3,4-fused 2-furyl-1,2,3,4-tetrahydroquinoline derivatives at the furan fragment according to the [4 + 2]-cycloaddition pattern. The reaction is not stereoselective, and it yields two diastereoisomeric 7-oxabicyclo[2.2.1]hepta-2,5-dienes whose structure was determined by X-ray analysis and NMR spectroscopy.     

Soluble and polymer-supported 2- and 3-benzylated furans for the preparation of α,β-ethylenic carbonyl compounds

Soluble and polymer-supported 2- and 3-benzylated furans were subjected to a sequence involving a Diels-Alder reaction with α,β-acetylenic carbonyl compounds, a Michael addition, and a subsequent retro-Diels-Alder reaction to yield olefinic compounds. On solid support, this traceless strategy is advantageous since pure compounds were released in the thermal cycloreversion step. The fur-2-ylated resin allowed a highly diastereoselective synthesis.     

Synthesis of polysubstituted furans via a novel and efficient heterocyclization approach

A new catalyst-free, one-pot synthesis of polysubstituted furans is reported. A series of [4-(4-aryl)-5-(cyclohexylamino)-2-(pyridin-2-yl)furan-3-yl](pyridin-2-yl)methanones was synthesized via multicomponent reaction of 1,3-di(pyridin-2-yl)propane-1,3-dione, aryl aldehydes, and cyclohexyl isocyanide.     

A one-pot three-component reaction for the preparation of highly functionalized tryptamines

We have developed a general one-pot method to provide highly functionalized tryptamine derivatives, via a Fischer indole type pathway. In this article, we demonstrate optimal conditions for a one-pot indole synthesis, allowing for the synthesis of a broad scope of 2-methyl tryptamine derivatives and a precursor for the synthesis of the core structure of some akuammiline alkaloids. Additionally, further modification of the indole products is described.     

A novel multicomponent reaction involving isocyanide, dimethyl acetylenedicarboxylate (DMAD), and electrophilic styrenes: facile synthesis of highly substituted cyclopentadienes

Alkyl isocyanides, DMAD, and various activated styrenes furnish fully substituted cyclopentadienes in a one-pot three-component reaction. [reaction: see text]     

A new titanium tetrachloride mediated annulation of alpha-aryl-substituted carbonyl compounds with alkynes: A simple and highly efficient method for the regioselective synthesis of polysubstituted naphthalene derivatives

A new straightforward procedure has been developed for the synthesis of polysubstituted naphthalene derivatives. The reaction of alpha-aryl-substituted carbonyl compounds with terminal or internal alkynes in the presence of TiCl4 regioselectively generates substituted naphthalene derivatives in good to excellent yields.     

Ni-catalyzed highly regio- and chemoselective cocycloaddition of nonconjugated diynes with 1,3-diynes: a novel method for polysubstituted arylalkynes

[reaction: see text] Effective nickel-catalyzed cocycloaddition of nonconjugated diynes with conjugated diynes yields polysubstituted arylalkynes in good to excellent yields with high regio- and chemoselectivity.     

One-pot, four-component reaction of isocyanides, dimethyl acetylenedicarboxylate, and cyclobutene-1,2-diones: a synthesis of novel spiroheterocycles

Isocyanides, dimethyl acetylenedicarboxylate, and cyclobutene-1,2-diones react in one-pot to afford novel spirocyclic compounds with double insertion of the isocyanide.     

Mannich-type reaction with trifluoromethylated N,O-hemiacetal: facile preparation of beta-amino-beta-trifluoromethyl carbonyl compounds

On treatment of silyl enolates and an N,O-hemiacetal, derived from trifluoroacetaldehyde ethyl hemiacetal and p-anisidine, with GaCl(3) (0.2 equiv) and C(6)H(5)COCl (0.2 equiv) in propionitrile, Mannich-type reaction took place smoothly to afford beta-amino-beta-trifluoromethyl carbonyl compounds in high yields.     

Phosphine-catalyzed domino reaction: an efficient method for the synthesis of highly functionalized spirooxazolines

A novel phosphine-catalyzed intermolecular [3 + 2] cycloaddition of ynones and N-substituted isatins was developed. In this reaction, substituted ynones, serving as a C(3) synthon, were successfully applied in intermolecular annulation reactions. A number of functionalized spirooxazolines were obtained in high yields and stereoselectivity.