Bicyclo undecene

The influence of solvents [64] and comparisons with catalysts of the diarylpro-linol series [65] were reported. For theoretical calculations on stereocontrol see Reference [66]. In addition, imidazolidin-4-one catalyzed cycloadditions have been used in several total syntheses of natural products. Intramolecular Diels-Alder reactions (IMDA) were reported as key steps in the synthesis of bicyclo-undecenes [67], amaminols [68], solanapyrones [69], telomerase inhibitor UCS1025A [70], englerin A [71], (-)-nor-platencin [72], and muironolide A [73]. In addition, asymmetric [3-1-2]-cycloadditions of azomethines were accomphshed in the presence of chiral imidazoUdinones [74]. Intermolecular cycloadditions of dihydropyridine 53 and acrolein catalyzed by imidazolidin-4-ones were reported. The chiral azabicyclo-octenol 54 was isolated as the important key intermediate in the total synthesis of lycopodium alkaloids [75] (e.g., ludduline) and oseltamivir (Scheme 4.19) [76]. 

In the presence of proton and/or Lewis acid and strong nucleophiles bicyclo[3.2.0]heptan-6-ones are converted to 3-substituted cycloheptanones (Table 15). Bicyclo[3.2.0]heptan-6-ones rearrange to give 3-iodocycloheptanones on treatment with iodotrimethylsilane. Zinc(II) iodide or mercury(II) halides as catalysts enhance the rate and the selectivity of the reaction.31 If a second, enolizable carbonyl group is present, an intramolecular alkylation may follow the ring enlargement under these reaction conditions.32 Consecutive treatment with tributyltin hydride/ 2,2 -azobisisobutyronitrile affords reduced, iodo-free cycloheptanones, whilst treatment with l,8-diazabicyclo[5.4.0]undecene yields cycloheptenones.33 Similarly, benzenethiol adds to the central bond of bicyclo[3.2.0]heptan-6-ones in the presence of zinc(II) chloride and hydrochloric acid under anhydrous conditions to form 3-(phenylsulfanyl)cycloheptanones.34... 

Titanium(IV) chloride-1,8-Diaza-bicyclo[5.4.0]undecene-7, 309 Titanium(IV) chloride-Diethylalu-minum chloride, 309 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Titanium(IV) chloride-4-Dimethyl-aminopyridine, 309... 

Majetich reports a general intramolecular Lewis acid allylation protocol for the synthesis of bicy-clo[5.4.0]undecen-3-ones (168) and bicyclo[4.4.0]decen-3-ones (170), which are 1,6-addition products (Scheme 27). The same precursors, (167) and (169), when submitted to the fluoride ion cyclization protocol, also afford 1,2- and 1,4-addition products.73 Typically, ethylaluminum dichloride, a proton sponge Lewis acid, is used in order to minimize adventitious protonic desilylation. Other 0,y-unsatu-rated silanes also undergo similar intramolecular Lewis acid catalyzed additions for example, the si-lylpropargylic enones (171) undergo intramolecular cyclization to the allenylspiro system (172).74... 

In the case of the cyclic substrate 51, the intervention of a C-H insertion pathway reveals itself in terms of the diastereoselectivity, not regioselectivity. Thus, exposure of enyne 51 to the standard Ru catalyst at ambient temperature produced the transfused bicyclo[5.4.0]undecene 52 (Equation 1.60, path a) [55]. If a metallacycle mechanism was operative, coordination of the metal with both the alkene and alkyne must occur to form the cis-fused product. On the other hand, coordination of the Ru with the Lewis basic bridgehead substituent directs it to abstract an allylic C-H on the same face as the substituent, which then leads to the trans-fused product as observed. On the other hand, cycloisomerization using a Pd(0) precatalyst does indeed lead to the Z-fused bicycle (Equation 1.60, path b). 

Entsprechend entsteht aus 4-Oxo-4H-chromen und Cyclopenten 8-Oxo-(benzo-3-oxa-tricyclo[6.3.0.02 ]undecen-(4)y 3. MitButin- (2) wird 7-Oxo-9,10-dimethyl-(3,4-benzo-2-oxa-bicyclo[4.2.0]ocladien-(3,7)y gcbildet1.2. und mit 1,1-Dimetkoxy-athylen ergibt sich 10,10-Dimethoxy-7-oxo-(benzo-2-oxa-bicyclo [4.2.0] ocfen-(J)) und 3,3-Dimethoxy-oxetan-(2-spiro-7y- 10,10-dime,lhoxy-(ljfMzo-2-oxa-bicyclo[4.2.0 octen-(3)y2>3. 

While studying the stereochemical outcome of the cyclization of an cu-iodo substituted link in disubstituted cyclooctadienic precursors, Winkler reported that the tra 5-disubstituted cyclooctadiene 105 led to the formation of a 1 1 mixture of cis-anti-cis and cis-syn-cis triquinanes 107 in 28% global yield and, as major products, trans- and cw-bicyclo[6.3.0]undecenes 108 (Scheme 31). This example reveals a complete lack of stereocontrol during the first 5-exo cyclization from radical 106 an exactly 1 1 trans, exjunction stereoselectivity is obtained [47],... 

Three different organic bases, imidazole (IM), triazole (TZ) and hydrogenated 1,8-diaza-bicyclo(5.4.0) undecene-7 (DBU) were immobilized on mesoporous materials. Immobilized state of organic bases and their catalytic activities in Knoevenagel condensation between ethylcyanoacetate and benzaldehyde was studied. Organic bases immobilized mainly on mesopore still retained their catalytic activities with an inevitable loss due to immobilization. Imidazole catalyst immobilized on KIT-1 disordered mesoporous material with three-dimensional channels showed a sufficient activity for multi-repeated use. 

Chem. Descrip. 1,8-Diaza-bicyclo (5.4.0) undecene-7 CAS 6674-22-2 EINECS/ELINCS 229-713-7 Uses Gelation catalyst for PU elastomers, shoe soles, coatings Features Very strong gelation provides R.T. cure highly active hydrolyzes in water... 

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