Preparation and characterization of 6-substituted 1,8-diazabicyclo[5.4.0]undec-7-ene

The lithium 1,8-diazabicyclo[5.4.0]undec-6-ide ( 1 ) prepared from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and n-butyllithium reacts with alkyl halides and carbonyl compounds such as benzophenone, acetophenone, and benzaldehyde to give 6-substituted DBU derivatives in good yields. The reaction behavior of 6-substi-tuted DBU was also investigated.     

Trifluoromethanesulfonate,trifluromethylsulfonylimide, and bis(trifluoromethylsulfonyl)imide salts and ionic liquids based on 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[ 4.3.0]non-5-ene

Trifluoromethanesulfonate, trifluoromethylsulfonylimide, and bis(trifluoromethylsulfonyl)imide salts and ionic liquids were synthesized from 2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepine (1,8-diazabicyclo[5.4.0]undec-7-ene) and 2,3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidine (1,5-diazabicyclo[4.3.0]non-5-ene). Their physicochemical properties, spectral parameters, and some chemical transformations were studied.     

Synthesis and Dimerization of Bicyclo [4.4.1] undec-1 (11)-ene,a Bridged trans-Cycloheptene

The synthesis of bicyclo [4.4.1] undec-1 (11)-ene ( 5 ) by intramolecular Wittig reaction is described. The Bredt olefin could not be isolated, but dimerized rapidly to a novel compound 15 containing a cyclopropane ring. The olefin 5 was trapped in situ by 2,5-diphenylbenzo [c]furan.     

Wagner-Meerwein skeletal rearrangement of 3-spiroannulated 6,8a-epoxy- and 6,8a;7,8-diepoxyisoquinolines (3-aza-11-oxatricyclo[6.2.1.0(1,6)]undec-9-enes). Isolation and identification of 5-aza-2-oxatricyclo[6.2.1.0(3,9)]undec-3-enes

The reactions of 3-acetyl-3-aza-11-oxatricyclo[6.2.1.0(1,6)]undec-9-ene and its 9,10-epoxy derivative with bromine and Ac(2)O/BF(3).OEt(2) under different conditions were studied. Unusual products of Wagner-Meerwein rearrangement bearing the olefin fragment (5-aza-2-oxatricyclo[6.2.1.0(3,9)]undecen-3-enes) were isolated and characterized by X-ray analysis.     

Rearrangement of a trishomocubane derivative to a tetracyclo[6.3.0.02,6.03,10]undec-4-ene

Reaction of 8,8,11,11-tetrafluoropentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane with idio trimethylsilane leads to the expectedd ₃-trishomocubane derivative, but reaction with the more electrophilic boron tribromide yields a tetracyclo[6.3.0.0^2,6.0^3,10]undec-4-ene derivative which was characterized by X-ray diffraction. The most easily visualized pathway for this transformation would be an initial rearrangement of the starting material to ad ₃-trishomocubane followed by additional bond breaking to form the undec-4-ene compound. Molecular mechanics calculations indicate the brominatedd ₃-trishomocubane is about 4 kcal/mol more stable than the brominated undec-4-ene molecule and the associated carbonium ions show the same ordering. These data would indicate an alternate reaction pathway must be operative; however, semiempirical calculations predict the reverse ordering of the above energies.     

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)-promoted efficient and versatile aza-Michael addition

A convenient and versatile method was developed for aza-Michael addition using a substoichiometric amount of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Various nitrogen nucleophiles were efficiently introduced to α,β-unsaturated carbonyl compounds employing 0.5 equiv of DBU. Furthermore, other heteroatomic nucleophiles could also be introduced successfully under the same reaction conditions.     

Palladium-catalysed dimerization of isoprene with carbon dioxide in the presence of organotin ethoxide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)

The palladium-catalysed dimerization of isoprene with carbon dioxide is promoted by treatment wiht tributyltin ethoxide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).     

Synthese und Molekülstruktur von [Al(SiMe3)3(DBU)] (DBU = 1,8-Diazabicyclo[5.4.0]undec-7-en)

Synthesis and Molecular Structure of [Al(SiMe₃)₃(DBU)] (DBU = 1,8-Diazabicyclo[5.4.0]undec-7-ene) [Al(SiMe₃)₃(OEt₂)] reacts with DBU (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) at 0 °C yielding [Al(SiMe₃)₃ · (DBU)] ( 1 ). 1 was characterised spectroscopically (¹H, ¹³C, ²⁹Si, ²⁷Al NMR, IR, MS) and by X-ray structure determination [monoclinic, C2/c, a = 33.053(2), b = 9.307(1), c = 20.810(1) Å, β = 124.07(2)°, V = 5302.4(5) ų, Z = 8, 218(2) K]. 1 does not react with [Cp₂ZrCl₂] even in boiling toluene.     

1,8-Diazabicyclo [5.4.0] undec-7-ene functionalized cellulose nanofibers as an efficient and reusable nanocatalyst for the synthesis of tetraketones in aqueous medium

Research on Chemical Intermediates - 1,8-Diazabicyclo [5.4.0] undec-7-ene functionalized cellulose nanofibers (CNF@DBU[Cl]) were simply prepared and characterized by analytical techniques. Scanning...     

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) as ligand for atom transfer radical polymerization (ATRP)

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) has been used as a bidentate ligand of copper (I) bromide for the ATRP of (meth)acrylates and styrene. With methyl methacrylate, the polymerization reached high conversions producing polymers with a good control of Mn and low polydispersity indexes (PDI = 1.19). Higher PDI were obtained with polystyrenes and poly(methyl acrylate)s. These results have been correlated to the redox properties of the catalytic complex.     

Synthetic study of diversifolin: the construction of 11-oxabicyclo[6.2.1]undec-3-ene core using ring-closing metathesis

Stereoselective synthesis of a potential intermediate bearing 11-oxabicyclo[6.2.1]undec-3-ene core, a common scaffold of biologically active germacrane-type sesquiterpenes, has been achieved. Synthetic features involve formal 1,3-asymmetric induction, unusual ring-closing metathesis constructing a 10-membered carbocycle system, and unique lactone transposition.     

Synthesis of 2-Norzizaene and 9,10-Dehydro-2-norzizaene (7,7-Dimethyl-6-methylidenetricyclo[6.2.1.01,5]undec-9-ene) via Intramolecular Allyl Cation Induced Cycloaddition

7,7-Dimethyl-6-methylidenetricyclo[6.2.1.0^1,5]undec-9-ene ( 10 ) has been prepared from allylic alcohol 8 in one step in 16% yield. Selective hydrogenation of 10 with diazene gives the 2-norzizaenes 1a and 11 .     

Synthesis and spectrophotometric study of deprotonation of octamethylporphyrin derivatives with 1,8-diazabicyclo[5.4.0]undec-7-ene in acetonitrile

Acidic properties of synthesized 5,10,15,20-tetrakis(4′-tert-butylphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin and 5,10,15,20-tetrakis(3′,5′-di-tert-butylphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin have been studied by spectrophotometry. Deprotonation of the intracyclic nitrogen atoms with 1.8-diazabicyclo [5.4.0]undec-7-ene in acetonitrile occurs in two steps. Deprotonation constants and ranges of the porphyrinsanionic forms existence have been determined, and influence of the peripheral substituents on acidic properties of the macrocyclic ligand has been elucidated.     

Thermal isomerization of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene through the (E,Z)-1,3-cycloheptadiene intermediate

The thermal isomerization of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene was studied using ab initio methods at the multiconfiguration self-consistent field level. The lowest-energy pathway for thermolysis of both structures proceeds through the (E,Z)-1,3-cycloheptadiene intermediate. Ten transition states were located, which connect these three structures to the final product, (Z,Z)-1,3-cycloheptadiene. Three reaction channels were investigated, which included the conrotatory and disrotatory ring opening of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene and trans double bond rotation of (E,Z)-1,3-cycloheptadiene. The activation barrier for the conrotatory ring opening of tricyclo[4.1.0.0(2,7)]heptane to (E,Z)-1,3-cycloheptadiene was found to be 40 kcal mol(-1), while the disrotatory pathway to (Z,Z)-1,3-cyclohetpadiene was calculated to be 55 kcal mol(-1). The thermolysis of bicyclo[3.2.0]hept-6-ene via a conrotatory pathway to (E,Z)-1,3-cycloheptadiene had a 35 kcal mol(-1) barrier, while the disrotatory pathway to (Z,Z)-1,3-cyclohetpadiene had a barrier of 48 kcal mol(-1). The barrier for the isomerization of (E,Z)-1,3-cycloheptadiene to bicyclo[3.2.0]hept-6-ene was found to be 12 kcal mol(-1), while that directly to (Z,Z)-1,3-cycloheptadiene was 20 kcal mol(-1).     

Thermal isomerizations of cis,anti,cis-tricyclo[7.4.0.0(2,8)]tridec-10-ene

cis,anti,cis-Tricyclo[7.4.0.0(2,8)]tridec-10-ene (13TCT) undergoes [1,3] sigmatropic rearrangements at 315 °C in the gas phase to the si product 1 and to the sr product 2 with si/sr = 2.1. The dominant thermal isomerization process, however, is epimerization at C8 to afford product 3. That stereomutation at C8 occurs 50% faster than the si and sr shifts combined.     

Nucleophilic catalysis with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) for the esterification of carboxylic acids with dimethyl carbonate

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) is an effective nucleophilic catalyst for carboxylic acid esterification with dimethyl carbonate (DMC). The reaction pathway of this new class of nucleophilic catalysis has been studied. A plausible, multistep mechanism is proposed, which involves an initial N-acylation of DBU with DMC to form a carbamate intermediate. Subsequent O-alkylation of the carboxylate with this intermediate generates the corresponding methyl ester in excellent yield. In the absence of DBU or in the presence of other bases, such as ammonium hydroxide or N-methylmorpholine, the same reaction affords no desired product. This method is particularly valuable for the synthesis of methyl esters that contain acid-sensitive functionality.     

Corner Bromination of 2-Methyl-endo-tricyclo[3.2.1.0(2,4)]octane and -oct-6-ene

Reaction of 2-methyl-endo-tricyclo[3.2.1.0(2,4)]octane (1) with bromine in CCl(4) gave 2-exo,3-endo-dibromo-2-endo-methylbicyclo[3.2.1]octane (3) which rearranges on silica to 2-exo,6-endo-dibromo-1-methylbicyclo[2.2.2]octane (4). Reaction in methanol gave 4-endo-bromo-2-exo-methoxy-2-endo-methylbicyclo[3.2.1]octane (10) and 4-endo-bromo-2-endo-methoxy-2-exo-methylbicyclo[3.2.1]octane (11) formed by corner attack of the bromine electrophile with C2-C4 bond rupture and inversion of configuration at the site of electrophilic attack. Reaction of 2-methyl-endo-tricyclo[3.2.1.0(2,4)]oct-6-ene (2) with bromine in CCl(4) and methanol gave products of reaction at the alkene site.     

Reactions of Nucleosides with 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU). Syntheses of N(3)-Methylene-Bridged Bis-uridines and Secouridine-Dinucleoside Analogs

Diasteroisomeric secouridine derivatives, appropriately protected and activated, served as starting compounds in the reactions with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in various solvents (CH₂Cl₂, MeCN, or dimethylformamide (DMF)). Reactions with DBU/CH₂Cl₂ gave N(3)-methylene-bridged bis-secouridines and bis-uridines (Scheme 3), while the reactions with DBU in non-alkylating solvents resulted in formation of secdinucleosides as the result of intermolecular ‘dimerizations’ (Scheme 2).     

Die photoisomerisierung von 3,6-hexanooxepin-4,5-dicarbonsäureestern zu tricyclo[6.2.1.0 1,5] undec-9-en-(3a,6-methanooctahydroazulen)-derivaten

Irradiation of the 3,6-hexanooxepins 1a – 1c affords the tricyclo[6.2.1.0^1,5] undec-9-ene(3a,6-methanooctahydroazulene)derivatives 2a – 2c in about 50% yield.     

The Non-planarity of the Bicyclo[2.2.1]hept-2-ene Double bond. Crystal Structures of Bicyclo[2.2.2]oct-2-ene,Bicyclo[2.2.1]hept-2-ene,and Bicyclo[2.1.1]hex-2-ene Systems

The crystal structures of (1R,4R,5S,8S)-9,10-dimethylidentricyclo[6.2.1.0^2,7]undec2(7)-ene-4,5-dicarboxylic anhydride ( 3 ), (1R,4R,5S,8S)11-isopropylidene-9,10-dimethylidenetricyclo[6.2.1.m^2,7]undec-2(7)-ene-4,5-dicarboxylic anhydride ( 6 ), (1R,4R,5S8S)-9,10-dimethylidenetricyclo[6.2.2.0^2,7]dodec-2(7)-ene-4,5-dicarboxylic anhydride ( 9 ), (1R4R5S8S)-TRICYCLO[6.2.2.0^2,7]dodeca-2(7), 9-diene-4,5-dicarboxylic anhydride ( 12 ) and (4R,5S)-tricyclo[6.1.1.0^2.7]dec-2(7)-ene-4,5-dicarboxylic acid ( 16 ) were established by X-ray diffraction. The alkyl substituents onto the endocyclic bicyclo[2.2.1]hept-2-ene double bond deviate from the C(1), C(2), C(3), C(4), plane by 13.5°4 in 3 and by 13.9° in 6 , leaning toward the endo-face. No such out-of-plane deformations were observed with the bicyclo[2.2.2]oct-2-ene derivatives 9 and 12 . The exocyclic s-cis-butadiene moieties in 3, 6 and 9 do not deviate significantly from planarity. The deviation from planarity of the double bond n bicyclo[2.2.1]hept-2-ene derivatives and planarity in bicyclo[2.2.2]oct-2-ene analogues is shown to be general by analysis of all known structures in the Cambridge Crystallographic Data File. The non-planarity of the bicyclo[2.2.1]hept-2-ene double bond cannot be attributed only to bond-angle deformations which would favour rehybridizatoin of the olefinic C-atoms since the double bond in the more strained bicyclo[2.1.1]hex-2-ene drivative 16 deviates from planarity by less than 4°.