1.5- Diazabicyclo undec

KETENES, KETENE DITffiRS AND RELATED SUBSTANCES] (Vol 14) 1,8-Diazabicyclo [5.4.0]undec-7-ene (DBU)... 

Strong bases such as methan olic potassium hydroxide, sodium methoxide, or 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), cause epimerization at the C-2 carbon or shift the beta-gamma double bond into conjugation with the lactone carbonyl (Fig. 4) (25,26). 

TBDMSCl, DMAP, Et3N, DMF, 25°, 12 h. " These conditions were used to silylate selectively a primaiy over a secondary alcohol. Besides DMAP, other catalysts such as 1,1,3,3-tetramethylguanidine, 1,8-diazabicy-clo[5.4.0]undec-7-ene(83-99%), l,5-diazabicyclo[4.3.0]non-5-ene, and ethyldiisopropylamine have been used. ... 

In addition to the perfluoroalkylzinc compounds, the zinc reagent formed from 1,1,1-trifluorotrichloroethane has received considerable attention. This zinc compound was first reported as a stable ether complex [56]. Later, the DMF complex was isolated and the structure was determined by X-ray diffraction and shown to be monomeric [57] (equation 50). This zinc reagent undergoes a variety of functionalization reactions, and some typical examples are illustrated in Table 2 [47, 58, 59, 60, 61] The alcohol products (Table 2) can be converted to AiCF=CXCF3 (X = Cl, F) by further reaction with diethylaminosulfur trifluoride (DAST) and l,8-diazabicyclo[5 4.0]undec-7-ene (DBU) [60]... 

Another procedure relies on a domino Michael-O-alkylation reaction sequence to yield a variety of dihydrofurans. Combination of cyclohexanedione (30) with vinyl bromide 50 in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) provides dihydrofuran 51 in 83% yield. Numerous 1,3-dicarbonyls and vinyl bromides are amenable to this methodology, and thus a wide range of products like 51 are available via this strategy. 

Addition of benzoyl chloride to 2.5-dimethyl-3,4,6-triphenyl-3//-azepine (13) in benzene in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) leads to elimination of hydrogen chloride and formation of the 2-methylene-l//-azcpine 14.117 All attempts to isomerize the methylene derivative to 1-benzoyl-2,5-dimethyl-3,4,6-triphenyl-l//-azepine under basic conditions failed. Analogous reactions can occur with 2,5-dielhyl-3,4,6-triphenyl-3//-azepine. 

Attempts to prepare 5-vinyl-5F7-dibenz[b,/]azepine by alkylation of 5i/-dibenz[b,/]azepine with 2-chloroethyl-p-toluenesulfonate followed by dehydrochlorination, or by direct vinylation with acetylene under pressure in toluene or in dimethyl sulfoxide, have failed.194 Also, 5H-dibenz[b,/]azepine fails to react with acryloyl chloride, although the 5-acryloyl derivative 8 (R = COCH = CH2 mp 122 — 123 C) has been prepared in 65% yield by condensing dibenz-azepine 5 with 3-chloroacryloyl chloride, followed by dehydrochlorination of the product with l,8-diazabicyclo[5.4.0]undec-7-ene in dimethyl sulfoxide at 80-90°C.194... 

The products are called 1,4-octasubstituted or 1,4,8,11,15,18,22,25-octasubstituted phthalocyanines. In this case only one structural isomer is possible. 3,6-Diheptylphthalonitrile when refluxed in pentan-1 -ol in the presence of nickel(II) acetate and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) for 48 hours yields the nickel phthalocyanine 16. 

The products are known as 2,3-octasubstituted or 2,3,9,10,16.17,23,24-octasubstituted phthalocyanines. As is the case for 1,4-octasubstituted phthalocyanines, only one structural isomer exists. Metal-free phthalocyanines 18 can be obtained by heating 4,5-disubstituted phthalonitriles 17 in a solvent containing a strong base such as l,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Ammonia can also be used as a base. 

Solvents of basic character or the addition of basic compounds such as l,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) to solvents like alcohols are often used in the preparation of soluble metal phthalocyanines 18. 

When 2,2-dimethylpropanal is used to prepare the azomethine moiety, the corresponding azaallyl anion may be obtained when l,8-diazabicyclo[5.4.0]undec-7-ene/lithium bromide is used as base. The subsequent addition to various enones or methyl ( )-2-butenoate proceeds with anti selectivity, presumably via a chelated enolate. However, no reaction occurs when triethylamine is used as the base, whereas lithium diisopropylamide as the base leads to the formation of a cycloadduct, e.g., dimethyl 5-isopropyl-3-methyl-2,4-pyrrolidinedicarboxylate using methyl ( )-2-butenoate as the enone84 89,384. 

Oxo-3,4-dihydro-2-quinoxalinecarbonitrile (153) gave A(-hydroxy-3-oxo-3,4-dihydro-2-quinoxalinecarboxamidine (153a) (H2NOH-HC1, pyridine, 6,8-diazabicyclo[5.4.0]undec-7-ene, EtOH, reflux, 2 h 96%). ... 

Cyclization of 148 with l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and a subsequent elimination reaction with acetic anhydride and pyridine furnished compound 149. °- Compound 149 was found to be an important key compound for the following synthesis of carba-sugars of the a-L-altro, fi-D-gluco, P-h-allo, and a-D manno modifications. 

Dendrimers 5-8 were obtained by taking advantage of the versatile regiose-lective reaction developed in the group of Diederich [24], which led to macro-cyclic bis-adducts of Cgg by a cyclization reaction at the C sphere with bis-mal-onate derivatives in a double Bingel cyclopropanation [25]. Reaction of the dendritic malonates with Cgg, I2, and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene at room temperature afforded the corresponding cyclization products 5-8 (Fig. 2). The relative position of the two cyclopropane rings in 5-8 on the Cgo core was determined based on the molecular symmetry deduced from the and NMR spectra (Cs) as well as on their UV/Vis spectra. It is well estabhshed... 

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