1,5-Diazabicyclo nonene-5

The elimination of HX from an alkyl halide is a very general reaction and can be accomplished with chlorides, fluorides, bromides, and iodides.232 Hot alcoholic KOH is the most frequently used base, though stronger bases233 (OR, NH2", etc.) or weaker ones (e.g., amines) are used where warranted.234 The bicyclic amidines l,5-diazabicyc o[3.4.0]nonene-5 (DBN)235 and l,8-diazabicyclo[5.4.0]undecene-7 (DBU)236 are good reagents for difficult cases.237... 

Butoxybis(dimethylamino)methane, 121 Dimethylformamide dimethyl acetal, 120 Trisdimethylaminomethane, 121 Marschalk reaction l,5-Diazabicyclo[4.3.0]nonene-5, 91 Meerwein-Ponndorf-Verley reduction Aluminum isopropoxide, 265 /-Butoxydiiodosamarium, 272 Dicyclopentadienyldihydridozirconium, 108... 

Isomerization of benzo[/]-l,5-diazabicyclo[3,2,2]nonene in 8.8 N HBr at 140°C yielded l,2,3,5,6,7-hexahydropyrido[l,2,3-de]quinoxaline (83 KGS677). Photolysis of dimethyl l-(quinolin-8-yl)-l,2,3-triazole-4,5-di-carboxylates in MeCN resulted in stable an/tydro-2,3-dimethoxycarbonyl-3//-pyrido[l,2,3-de]quinoxalin-4-ium hydroxides [87JCS(P1)403]. 6-Hy-droxymethyl-2-methyl-7-methoxy-l,2,3,4-tetrahydro-6//-pyrazino-[1,2-h]isoquinolin-4-one (138) was prepared from 5- [A-methyl-Ar-(ethoxy-... 

Unlike the model system, (66) could not be brominated directly. Therefore, it was converted into the ketone (67) by heating in 80% acetic acid, and this ketone was brominated with excess bromine in ether to give (68). Conversion of (68) into the acetal (69) was accomplished with diethylene orthocarbonate and toluene-p-sulphonic acid. Rearrangement of (69) to (70) was effected by heating with excess 1,5-diazabicyclo[3,4,0]nonene in xylene-DMSO. On comparison of i.r., n.m.r., and mass spectral data, this synthetic racemate was identical with the corresponding derivative from natural chasmanine. 

Two frequently used amidine bases are DBN (l,5-diazabicyclo[3.4.0]nonene-5) and DBU (l,8-cfiazafciicyclo[5.4.0]undecene-7). 

Chapter S you met the bases DBU (l,8 diazabicyclo[5.4.0]undecene-7) and DBN (l,5-diazabicycio[3.4.0]nonene-5) named in the same way—and you will meet them again in the very next chapter, as they are particularly good bases for the promotion of elimination reactions. 

Methyl acrylates." The reagent is converted by LDA into the stable ester enolate a, which is alkylated by primary alkyl iodides and allylic bromides in the presence of HMPT to give the useful Mannich bases 2. These products can be converted into methyl acrylates (4) by quaternization (quantitative) followed by treatment with diazabicyclo[4.3.0]nonene-5 (DBN) in refluxing benzene. 

The same sequence was also used to prepare the labile phenanthrene 3,4-oxide except that in this case sodium mechoxide was replaced by l,S-diazabicyclo[4.3.0]-nonene-5 (DBN, this volume). 

BASES Ascarite. Barium hydroxide. 1,8-Bis(dimethylamino)naphthaIene. n-Butyl-amine. I, S-Diazabicyclo 4.3.0]nonene-5 (DBN). l,4-Diazabicydo 2.2.2]octane-... 

ETHYLENETHIOKETALS Chloramine-T. E/C-GLYCOLS Ceric ammonium nitrate. METHYL ESTERS 1,5-Diazabicyclo-14.3.0] nonene-5. 1,5-Diazabicyclo[5.4.0]-undcccnc-5... 

One step in a synthesis of dl-muscone (4) from exaltone (1) involved dehydrobromina-tion of (2). This was effected with l,5-diazabicyclo[4.3.0]nonene-5 in 70% yield. Treatment with potassium r-butoxide in 7-butanol or DMSO afforded only the dioxine (5).2... 

Cyclizatioa. In a synthesis of (+ )-/J-copaene (3) Corey and Watt6 effected cycliza-tion of (1) to the tricyclic ketone (2) with this reagent. Use of potassium r-butoxide or l,5-diazabicyclo[4.3.0]nonene-5 proved unsuccessful. 

Dehydrohalogenation Benzyltrimethylammonium mcsitoate. r-Butylamine. Calcium carbonate. j Uidine. Diazabicyclo[3.4.0]nonene-5. N.N-Dimethylaniline (see also Ethoxy-acetylene, preparation). N,N-Dimelhylformamide. Dimethyl sulfoxide-Potassium r-but-oxide. Dimethyl sulfoxide-Sodium bicarbonate. 2,4-Dinitrophenylhydrazine. Ethoxy-carbonylhydrazine. Ethyldicyclohexylamine. Ethyidiisopropylamine. Ion-exchange resins. Lithium. Lithium carbonate. Lithium carbonate-Lithium bromide. Lithium chloride. Methanolic KOH (see DimethylTormamide). N-PhenylmorphoKne. Potassium amide. Potassium r-butoxide. Pyridine. Quinoline. Rhodium-Alumina. Silver oxide. Sodium acetate-Acetonitrile (see Tetrachlorocyclopentadienone, preparation). Sodium amide. Sodium 2-butylcyclohexoxide. Sodium ethoxide (see l-Ethoxybutene-l-yne-3, preparation). Sodium hydride. Sodium iodide in 1,2-dimethoxyethane (see Tetrachlorocyclopentadienone, alternative preparation) Tetraethylammonium chloride. Tri-n-butylamine. Triethylamine. Tri-methyiamine (see Boron trichloride). Trimethyl phosphite. 

Diels-Alder dienes 1-Acetoxybutadiene. Butadiene. Cyclopentadiene. (rans,mins-l,4-Diacetoxybutadiene. 2,5-Di-o-anisyl-3,4-diphenylcyclopentadienone. 5,5-Dimethoxy-l, 2,3,4-tetrachlorocyclopentadienone. 2,3-Dimethylbutadiene. 6,6-Dimethylfulvene (see o-Acetoxy acrylonitrile). 2,4-Dimethyl-l,3-pentadiene (see Diethyl azodicarboxylate). 2,3-Diphenyl-butadiene. 1,3-Diphenylisobenzofurane (see Potassium I-butoxide). rrans,/nus-l,4-Diphenyl-butadiene. 1,3-Diphenylisobenzofurane. Hexachlorocyclopentadiene. Isobenzofurane. l-o-Nitrophenylbutadiene-1,3. Oxepin (see Diazabicyclo[3.4.0]nonene-S). Phenylcyclone. Piperylene. n-Pyrone (see also Methyl vinyl ketone). Tetrachlorocyclopentadienone. Tetra-chlorofurane. Tetraphenylcyclopentadienone. 

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