Potassium I-butoxide

Only two general methods have been developed for the synthesis of the macrocyclic annulenes.9 The first of these, developed by Sondheimer and co-workers, involves the oxidative coupling of a suitable terminal diacetylene to a macrocyclic polyacetylene of required ring size, using typically cupric acetate in pyridine. The cyclic compound is then transformed to a dehydroannulene, usually by prototropic rearrangement effected by potassium i-butoxide. Finally, partial catalytic hydrogenation of the triple bonds to double bonds leads to the annulene. 

The yield of 11,ll-dichlorotricyclo[4.4.1.01,6]undeca-3,8-diene strongly depends on the quality of the potassium <-butoxide used. Commercially available, sublimed potassium i-butoxide was employed. When freshly sublimed potassium f-butoxide is utilized, yields of up to 45% of 11,ll-dichlorotricyclo[4.4.1.01- ]undeca-3,8-diene can be obtained. Potassium <-butoxide, prepared by the method of Doering, gave yields comparable to those achieved with the commercial product. 

Commercial potassium I-butoxide is used directly as obtained from the Mine Safety Appliance Research Corp., Gallery, Pennsylvania. 

The pyrrolizinium salts 264a,128 264b,67 and 26567 have been cyclized by aqueous ammonia to give the [2.2.3]cyclazines 306-308. Compound 264a also reacted with nitromethane and potassium i-butoxide to give the nitro[2.2.3]cyclazine 309.128 [2.2.3]Cyclazines 313-315 can also be made from 3f/-pyrrolizines and the vinylamidinium salts 311 and 312.87 Cyclazine... 

For example, reaction of 2,3-diphenyl-5-(jp-tolyl)furan (30) with Schiff s base derived from benzaldehyde and p-chloroaniline in the presence of potassium hydroxide at 60°-65°C yields the stilbenylfuran 31 28,27 Moreover, at 90° to 95°C in the presence of potassium i-butoxide... 

As was found in the case of the methyl-substituted 2-phenylbenzo-[2>]furans (cf. 34), a similar variation in the reactivity of the methyl groups in 3,5-di(p-tolyl)-1,2,4-oxadiazole (63) has also been observed.11 With benzalaniline in the presence of potassium hydroxide the 5-(stilben-4-yl)-3-0-tolyl)-l,2,4-oxadiazole (64) is formed, whereas with potassium i-butoxide both methyl groups react, leading to 3,5-di(stilben-4-yl)-l,2,4-oxadiazole (65). Some further stilbene derivatives of 1,2,4-oxadiazoles are shown in Table V. 

Nucleophilic cleavage by potassium i-butoxide of digermanes, distannanes and diplum-banes in N, /V -dimethylpropyleneurea (DMPU) as solvent provided a facile and general... 

Potassium acetate, reaction with N,N-dichlorocyclohexylamine, 46,17 Potassium i-butoxide, 46, 33... 

A novel reaction of quaternary AT-methylphosphazenium iodides, [N P Me2n+i] Ie(n = 3, 4), with sodium bis(trimethylsilyl)amide has been reported. Phosphorines with exocyclic methylamino groups are formed as a result of phosphazene ring cleavage. Similar cleavage occurs in the reaction of quaternary phosphazenium iodides with potassium-i-butoxide (97). 

This reaction has been considered above (method 184) with respect to ease of mono- and di-alkylation. A large number of condensing agents have been compared, including sodium and potassium ethoxide, sodium in dioxane or toluene, sodium hydride, sodium amide, and sodium or potassium i-butoxide. In general, sodium ethoxide is recommended in the alkylation of acetoacetic ester with primary halides (73%) potassium ethoxide with branched halides, such as isobutyl and s-butyl halides... 

CycUzation, In a synthesis of ( )-/Stricyclic ketone (2) with this reagent. Use of potassium i-butoxide or I,5-diazabicyclo[4.3.0]noncne-5 proved unsuccessful. 

Benzocyclopropene. ° Benzocyclopropene (3) can be prepared conveniently in two steps. 1,4-Cyclohexadiene (I) is treated with dichlorocarbene (generated from chloroform and potassium (-butoxide) to give 7,7-dichlorobicyclo[4.1.0]heptene-3 (2) in 41 % yield. This intermediate is then treated with potassium i-butoxide and D VTSO... 

Intramolecular palladium-catalyzed cyclization reactions have also been used to synthesize pyrazole derivatives. iV-Aryl-iV-(o-bromobenzyl)hydrazines 494 participated in a palladium-catalyzed intramolecular amination reaction to give 2-aryl-2//-indazoles 495 (Equation 101) <20000L519>. Palladium-catalyzed intramolecular C-N bond formation of iV-acetamino-2-(2-bromo)arylindolines 496, followed by hydrolysis and air oxidation in the presence of aluminium oxide, allowed the preparation of indolo[l,2-3]indazoles 498 via intermediate 497 (Scheme 58) <2002TL3577>. 3-Substituted pyrazoles have been prepared from the intramolecular cyclization of A -tosyl-iV-(l-aryl/ vinyl-1-propyn-3-yl)hydrazine and then exposme of the reaction mixture of the cyclization to potassium /i //-butoxide <1997SL959>. iV-Aryl-iV -(o-bromobenzyl)hydrazines 499 or [A -aryl-A -(t>-bromobenzyl)hydrazinato-A ]-triphenyl-phosphonium bromides 501 participated in a palladium-catalyzed intramolecular amination reaction to give 1-phenyl-l//-indazoles 500 (Scheme 59) <2001TL2937>. 

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. 

Tosylate rearrangement. Mazur devised an ingenious scheme for the synthesis of perhydroazulenes and first explored the stereochemistry by applying the reaction in the steroid series. Cholestane-5a,6a-diol 6-tosylate (1) is converted quantitatively into the A-homo-B-nor-5-ketosteroid (2) when refluxed with finely divided calcium carbonate-dimethylformumide for 6-8 hrs. or heated with potassium i-butoxide in f-butanol at 100°, C holeNtune-4( ..5 -diol 4-tosylate (3) gave A-nor-B-homo-.5-... 

A. Potassium t-butoxide. To 500 ml. of <-butyl alcohol (Note 1) in a 3-1. three-necked flask equipped with an efficient sealed stirrer, a nitrogen inlet (Note 2), a 500-ml. dropping funnel with a pressure-equalizing side tube (Note 3), and a reflux condenser there is added 20 g. (0.5 g. atom) of clean potassium metal. After the potassium has reacted, the condenser is replaced by a 12-in. distillation column and the excess i-butyl alcohol is removed by distillation until crystals begin to form in the solution. There is added 2 1. of dry heptane and the distillation is continued until the head temperature reaches 98° (Notes 4 and 5). The residual mixture is adjusted to a 1.5-1. volume by addition of dry heptane and the resulting slurry of potassium i-butoxide in heptane is cooled to 0-5° in an ice bath (Note 6). 

This amount of potassium I-butoxide is not soluble in the dimethylsulfoxide at a lower temperature. An excess of base over I-butyl alcohol is necessary to the reaction, and a high concentration of I-butyl alcohol (3.33/) considerably improves the yield of product desired. 

An interesting rearrangement of some 2,4-diazabicyclo[4,2,0]oct-7-ene-3,5-diones (138) by reaction with potassium i-butoxide gave the corresponding 2-pyridones and l,3-dioxo-l,2,3,4-tetra-hydropyrrolo[l,2-c]imidazoles (139) (Equation (12)) <83JOC2337). 

Independently 14) it has been shown that the Oppenauer oxidation of the base XXIII (R = CH20H) with potassium i-butoxide and benzophenone in benzene in the strict absence of air gives norfluorocurarine (XXIV) as the major product although some of the aldehyde XXIII (R = CHO) is formed, it shows no strong tendency to oxidize in air. Norfluorocurarine must therefore be the direct product of Oppenauer oxidation of XXIII (R = CH20H). 

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