Reaction of 3-aminoindole-2-carboxylic acids with diethyl acetylenedicarboxylate

-Carboline and indolo--carboline derivatives were obtained by reaction of the potassium salts of 3-aminoindole-2-carboxylic acids with diethyl acetylenedicarboxylate. A difference in the behavior of 3-aminoindole derivatives in the Michael reaction due to the nature of the substituent in the 5 position of the indole ring was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 82–84, January, 1977.     

Studies on the catalysis of the reaction of organotin phenoxides with diethyl acetylenedicarboxylate

Different organotin phenoxides react at room temperature with diethyl acetylenedicarboxylate in diethyl ether, in the presence of lithium perchlorate to give a mixture of corresponding phenyl vinyl ethers and ring ethenylated phenols. Copyright © 2005 John Wiley & Sons, Ltd.     

Sustainable radical reduction through catalytic hydrogen atom transfer

A system with coupled catalytic cycles is described that allows radical reduction by hydrogen atom abstraction from rhodium hydrides. These intermediates are generated from H2 activation by Wilkinson's catalyst. Radical generation is carried out by titanocene-catalyzed electron transfer to epoxides.     

Lewis acid promoted phenylseleno group transfer tandem radical cyclization reactions

[reaction: see text] A new Lewis acid promoted phenylseleno group transfer tandem radical cyclization method was developed. In the presence of Lewis acids such as Yb(OTf)3 or Mg(ClO4)2, under photolysis condition at low temperature (-45 degrees C), various unsaturated alpha-phenylseleno beta-keto amides underwent radical cyclization reactions to give monocyclic or bicyclic products in a highly efficient, regioselective, and stereoselective manner.     

Atom transfer radical polymerization through N‐chlorosulfonamides

Controlled polymerizations of vinyl monomers such as methyl methacrylate and styrene are achieved using N‐chloro,N‐propyl‐p‐toluenesulfonamide (NCPT) together with a cuprous bromide/hexahexyl triethylenetetramine (CuBr/H‐TETA) complex. Although N‐halosulfonamides are known to decompose radically to give free chlorine, NCPT alone (without a cuprous complex) does not initiate any polymerization even in prolonged reaction times. Instead these add to the double bonds to give 2‐chloroethylsulfonamides. In the present polymerization system a good chlorine donator (NCPT) is combined with an organic soluble complex (CuBr/H‐TETA) to perform atom transfer radical polymerizations (ATRPs) in homogenous conditions. The linear proportionality of the molecular weights to the conversions and straight lines observed in ln(M₀/M) (where M₀ and M are the monomer contents at the beginning and at any time, respectively) versus time plots indicate typical controlled polymerization characteristics. The use of freshly prepared NCPT is advisable due to its slow and spontaneous decomposition when standing at room temperatures. Because of their easy preparation, N‐chlorosulfonamides can be used and are preferred instead of special halogen compounds commonly used in copper mediated ATRP. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2691–2695, 2001     

A xanthate transfer radical process for the introduction of the trifluoromethyl group

[reaction: see text]. S-Trifluoromethyl xanthates efficiently add to unactivated alkenes by a radical mechanism to give adducts with a trifluoromethyl group at the least hindered terminus of the olefin.     

Cycloaddition reaction of 2‐allenylindoles with diethyl acetylenedicarboxylate under thermal and high pressure conditions

The cycloaddition reaction of 2‐allenylindoles 2 with diethyl acetylenedicarboxylate 6 was undertaken under both thermal and high pressure reaction conditions, leading to carbazole derivatives 5 .     

Densely grafting copolymers of ethyl cellulose through atom transfer radical polymerization

Densely grafting copolymers of ethyl cellulose with polystyrene and poly(methyl methacrylate) were synthesized through atom transfer radical polymerization (ATRP). First, the residual hydroxyl groups on the ethyl cellulose reacted with 2‐bromoisobutyrylbromide to yield 2‐bromoisobutyryloxy groups, known to be an efficient initiator for ATRP. Subsequently, the functional ethyl cellulose was used as a macroinitiator in the ATRP of methyl methacrylate and styrene in toluene in conjunction with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst system. The molecular weight of the graft copolymers increased without any trace of the macroinitiator, and the polydispersity was narrow. The molecular weight of the side chains increased with the monomer conversion. A kinetic study indicated that the polymerization was first‐order. The morphology of the densely grafted copolymer in solution was characterized through laser light scattering. The individual densely grafted copolymer molecules were observed through atomic force microscopy, which confirmed the synthesis of the densely grafted copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4099–4108, 2005     

Reactions of salicyl N-tosylimines or salicylaldehydes with diethyl acetylenedicarboxylate for the synthesis of highly functionalized chromenes

Reactions of diethyl acetylenedicarboxylate with salicyl N-tosylimines or salicylaldehydes proceeded smoothly in the presence of DABCO or dimethylphenylphosphine under mild conditions to give the corresponding chromenes in excellent yields.     

Intramolecular carbozincation of unactivated alkenes occurs through a zinc radical transfer mechanism

The cyclizations of a number of terminally unsaturated alkenyl zinc iodides to cyclopentylmethylzinc iodides, formerly believed to be nonradical in nature, have been revealed as radical chain cyclizations initiated by adventitious oxygen. Five cases are presented in which the published carbozincation cis/trans selectivities are essentially the same as those found for the cyclizations of the unsaturated alkyl iodide precursors of the alkylzinc iodides by the iodine atom transfer method at approximately the same temperatures. In addition, it has been found that one of the organozinc cyclizations does not occur in a system in which oxygen has been rigorously excluded. The combined findings strongly suggest that these organozinc cyclizations occur by a zinc radical transfer mechanism rather than by a conventional carbometallation that is thought to occur with the analogous organolithium and organomagnesium cyclizations.     

Unprecedented copper(I)-catalyzed photochemical reaction of diethyl ether with vicinal diols and ketals

A novel Cu(I)-catalyzed photochemical reaction of diethyl ether with vicinal diols and their ketals is reported. The most remarkable feature is the transformation of 1,2-diols and their ketals to acetals of acetaldehyde under totally neutral condition without using acetaldehyde.     

Reaction of arylamidoximes with dimethyl acetylenedicarboxylate and diethyl chlorofumarate. Stereochemistry of the adducts and the derived 1,2,4-oxadiazines

It was shown that the addition of benzamidoxime to dimethyl acetylenedicarboxylate was predominantly cis-oid in methanol or acetonitrile solution and mainly trans-oid when benzene was the solvent. The stereochemistry of the cis-oid ( 4a ) and trans-oid ( 5 ) adducts was deduced by transformation into the oxadia-zinones ( 7a and 8a ) which, upon hydrolysis and subsequent reaction with acetic anhydride, gave the furo-[2,3-c]-1,2,4-oxadiazine ( 9 ) and the symmetrical anhydride ( 10 ), respectively. The reaction of diethyl chlorofumarate with the sodium salt of benzamidoxime produced the oxadiazinone ( 8c ).     

Et2AlCl-promoted asymmetric phenylseleno group transfer radical cyclization reactions of unsaturated beta-hydroxy esters

We have developed a new method for asymmetric phenylseleno group transfer radical cyclization of unsaturated beta-hydroxy esters. Various unsaturated alpha-phenylseleno beta-hydroxy esters underwent radical cyclization in the presence of Et(2)AlCl in benzene with sunlamp irradiation at 25-30 degrees C to give mono- and bicyclic group-transferred products in an efficient and highly regioselective and diastereoselective manner. To rationalize the high diastereoselectivities observed in this reaction, we propose a model based on chelation control of the aluminum alkoxides that are formed in situ. We devised a general method to prepare chiral radical precursors from which we obtained highly optically pure mono- and bicyclic group transfer products. The synthetic advantages of this method are demonstrated by our formal total synthesis of (-)-wilforonide. This paper presents the first examples of stereoselective group transfer radical cyclizations that occur via 1,2-asymmetric induction.     

Sustainable radical reduction through catalyzed hydrogen atom transfer reactions (CHAT-reactions)

A system with coupled catalytic cycles is described that allows radical reduction by catalyzed hydrogen atom transfer (CHAT) from transition metal hydrides. These intermediates are generated through H₂ activation. Radical generation is carried out by titanocene catalyzed electron transfer to epoxides. The reaction provides a novel entry into the atom-economical reduction of radicals that has long been considered as a critical issue for the industrial application of radical chemistry.     

Intramolecular electron transfer initiated cation and radical formation through carbon-carbon bond activation

Radical cations can be formed in a spatially and temporally controlled manner by appending a sacrificial photooxidant to an easily oxidized substrate, leading to intramolecular electron transfer upon irradiation. The anthraquinone carboxyl group is an effective photooxidant that can promote single electron oxidation from an appended arene. The resulting intermediates undergo a cleavage reaction through carbon-carbon bond activation to provide either cations or radicals that react to form a range of products.     

Effect of group electronegativity on electron transfer in bis(hydrazine) radical cations

The radical cation of 4,10-ditert-butyl-5,9-diisopropyl-4,5,9,10-tetraazatetracyclo[6.2.2.2]-tetradecane (sBI4T(+)), as well as its substituted bis(hydrazine) radical cations, is chosen for the investigation of the electronegativity dependence of its intramolecular electron transfer. To do so, two parameters, reorganization energy and electronic coupling, are calculated with several ab initio approaches. It is found that the electronic couplings decrease with the increase of the group electronegativity while the reorganization energies do not show an explicit dependency. Furthermore, Marcus formula is employed to reveal those effect on the electron transfer rates. The predicted rates of electron transfer generally decrease with increasing group electronegativity, although not monotonically.     

Formation of peptide radical ions through dissociative electron transfer in ternary metal-ligand-peptide complexes

The formation and fragmentation of odd-electron ions of peptides and proteins is of interest to applications in biological mass spectrometry. Gas-phase redox chemistry occurring during collision-induced dissociation of ternary metal-ligand-peptide complexes enables the formation of a variety of peptide radicals, including the canonical radical cations, M(+?), radical dications, [M+H](2+?), radical anions, [M-2H](-?) and phosphorylated radical cations. In addition, odd-electron peptide ions with well-defined initial location of the radical site are produced through side-chain losses from the radical ions. Subsequent fragmentation of these species provides information regarding the role of charge and location of the radical site on the competition between radical-induced and proton-driven fragmentation of odd-electron peptide ions. This account summarizes current understanding of the factors that control the efficiency of the intramolecular electron transfer (ET) in ternary metal-ligand-peptide complexes resulting in formation of odd-electron peptide ions. Specifically, we discuss the effect of the metal center, the ligand and the peptide structure on the competition between the ET, proton transfer (PT) and loss of neutral peptide and neutral peptide fragments from the complex. Fundamental studies of the structures, stabilities and the energetics and dynamics of fragmentation of these complexes are also important for detailed molecular-level understanding of photosynthesis and respiration in biological systems.     

Fabrication of thermosensitive polymer nanopatterns through chemical lithography and atom transfer radical polymerization

Micro- and nanopatterns of thermosensitive poly(N-isopropylacrylamide) brush on gold substrate were prepared by using chemical lithography combined with surface-initiated atom transfer radical polymerization. Self-assembled monolayers of 4'-nitro-1, 1'-biphenyl-4-thiol were structured by chemical lithography which produced cross-linked 4'-amino-1,1'-biphenyl-4-thiol monolayer within a nitro-terminated matrix. The terminal amino groups in monolayers were bounded with the surface initiator bromoisobutyryl bromide. After polymerization, the smallest size can reach to 70-nm line width and dots. The thermosensitivity of poly(N-isopropylacrylamide) brushes is demonstrated by contact angle measurement and fluid atomic force microscopy. This fabrication approach allows creating spatially defined polymer patterns and provides a simple and versatile method to construct complex micro- and nanopatterned polymer brushes with spatial and topographic control in a single step.