Potassium rm-butoxide

The 5,10-epoxy[10]annulene system readily undergoes addition of bromine with formation of an epoxide across the central bond. By dehydrohalogenation the annulene structure can be restored. For example, the dibromo and tetrabromo adducts of 5,10-epoxy[10]annulene can be converted with potassium rm-butoxide to l-bromo-5,10-epoxy[10]annulene (13) and 1,6-dibromo-5,10-epoxy[10]annulene (14), respectively.159... 

Treatment of 10-bromodibenz[fe,/]oxepin with potassium rm-butoxide at 100 C in dioxane results in elimination of hydrogen bromide to give 10,11-didehydrodibenz[6,/ oxepin. This highly strained alkyne intermediate can be trapped with dienophiles, for example, with 2,5-dimethylfuran to give 4.160... 

An alternative synthesis of 9//-tribenz.[/ >,ia, /]azepine (65, R = H) involves cycloaddition of 10,1 l-dehydro-5i/-dibenz[/t,/]azepine (66), generated from 5-acetyl-10-bromo-5//-dibcnz[/ ,/]azepine, with cyclohexa-1,3-diene.8 The cycloadduct 67, so-formed, with potassium rm-butoxide in refluxing bis(2-methoxyethyl) ether (diglyme) undergoes hydrolysis and loss of ethene to give the tribenzazepine in 39% yield. 

The heteroaryne 15. produced by treating 5-aeetyI-10-bromo-5//-dibenz[/>,/]azepine (14) with potassium rm-butoxide (see Section 3.2.1.4.2.), has been trapped by cyclohexa-1,3-diene8 and by furan118 as the [4 + 2] cycloadducts 16 and 17, respectively (see also Section 3.2.1.1.1.1.).118... 

When chloromethylsulfinylmethane is reacted with unsymmetrical ketones in the presence of potassium rm-butoxide in fert-butanol, diastereomeric mixtures of oxiranes are formed, showing that the asymmetric induction at the prostereogenic carbonyl carbon atom is low21. 

To a stirred solution of (1.5 mmol) of LDA in 3.5 mL of THF/hcxane (60 40) at — 78 C under a nitrogen atmosphere is added 198 mg (1.5 mmol) terf-butyl propanoate in 1.5 mL of HMPA. After 30 min 169 mg (1.5 mmol) of potassium rm-butoxide are added and the mixture is stirred for 10 min. Then 133 mg (0.5 mmol) of ethyl 6-iodo-2-hcxcnoatc in 1.5 mL of TI1F arc added and the mixture is stirred for an additional 0.5 h at — 78 C. The reaction is quenched by adding sat. aq NH4C1. Extraction with ethyl acetate, drying over Na,S04 followed by evaporation of the solvent and short-path distillation gives the adduct yield 135 mg (100%). 

Indene, however, does give four-membered ring adducts with PTAD,69 and phthalazine-t,4-dione.70 The reaction with PTAD proceeds stepwise via the dipolar intermediate 43, which was trapped in the presence of water to give 44, under conditions in which the 1,2-diazetidine (45) was not opened by water to 44 (Scheme 5).69 Hydrolytic cleavage of the triazole ring in 45 using potassium rm-butoxide in wet dimethyl sulfoxide, followed by... 

FIGURE 25. The heterogeneous gas-phase dehydrochlorination of /1-chloroethyazide on solid potassium rm-butoxide yielding vinyl azide, and the subsequent thermal decomposition of the latter to 27/-azirine. The double-oven apparatus is equipped with cold traps for the by-product tert-butyl alcohol and the end product 2/7-azirine. The PES ionization patterns of the pure compounds were used for optimization of the reaction conditions. Reproduced by permission of Verlag der Zeitschrift der Naturforschung from Reference 215... 

Problem 7.45 Potassium rm-butoxide, K+OCMe3, is used as a base in E2 reactions, (a) How does it compare in effectiveness with ethylamine, CH3CH2NH2 (b) Compare its effectiveness in the solvents tert-butyl alcohol and dimethylsulfoxide (DMSO). (c) Give the major alkene product when it reacts with (CH3)2CC1CH2CH3. ... 

In a related context, 2-(/Koiuenesulfonyl)ethy]amine was used as an ammonia equivalent in an aza-ene reaction by which aldehyde 92.1 was converted to the bicycle 912 [Scheme 8.92].223 After N-acetylation and Pd(0)-catalysed hydro-stannylation, the alkenylstannane 914 dintensed under copper(II) nitrate catalysis. The 2-(p-toiuenesulfonyl)ethyl group was then discharged by p-elimination with potassium rm-butoxide. 

Vinyl, ally] and homoallyl derivatives of germanium and tin also form the corresponding cyclopropanes with dichlorocarbene generated by the chloroform/potassium rm-butoxide or bromodichloromethyl(phenyl)mercury methods (Table 23).265... 

Table 34. 1,1-Diiodocyclopropanes from Diiodocarbene, Generated from Iodoform and Potassium rm-Butoxide, and Alkenes...

O-rm-Butyl trichloroacetimidate. prepared in 70% yield by reacting potassium rm-butoxide with trichloroacetonitrile. reacts with carboxylic acids and alcohols in the presence of a catalytic amount of boron trifluoride etherate at room temperature in cyclohexane-dichloromethane [Scheme 6.3S]. 7 The method also converts alcohols to ferr-butyl ethers (see section 4.3.2). A very similar reaction that allows rerr-butylation under essentially neutral conditions on a large scale involves reaction of a carboxylic acid with 3-4 equivalents of N,V-di-isopropyl-0-/er/-butylisourea [Scheme 6.36]. The reaction proceeds via a tertiary carbocation ion intermediate and since capture of the cation is inefficient, excess isourea is required. The presence of alcohols is tolerated but not thiols or unhindered amines. The reaction conditions are compatible with a range of acid sensitive groups such as N-trityl derivatives and cyclopentylidene acetals. ... 

Synthesis of a vinyl cyclic acetal monomer is similar to the synthesis of a NVGA but includes a dehydrohalogenation step as shown in Figure 4. Stoichiometric amounts of the appropriate aryl aldehyde and 3-chloropropane-l,2-diol were reacted and worked up as previously described. The chloromethyl cyclic acetal intermediate was dissolved in toluene and added slowly to three equivalents of potassium rm-butoxide in toluene in a round bottom flask cooled in an ice bath. When the addition was complete, the mixture was allowed to warm to room temperature and stirred vigorously overnight. The dark reaction mixture was vacuum filtered through a paper filter covered with a small amount of silica gel. The filtrate was dried and concentrated as before. 

Because the pKa of p-methoxyphenol allows a full deprotonation by potassium rm-butoxide, it is suggested that the propagation results from nucleophilic attack of the phenoxide on an intermediate quin-odimethane formed by dehydrohalogenation of the monomer. Polymerization under these conditions is found to yield polymers with very low polydispersity values [26]. 

The ease of synthesis of the N-hydioxypynolo[3,2- ]pyridine offered an opportunity to prepare the conesponchng N-aikoxy compounds. Treatment of the N hydroxy compounds, 28, with potassium rm-butoxide followed by addition of methyl iodide or allyl bromide afforded in high yield, N-methoxy- and N-allyloxypyrrolo[3,2-ft]pyridines 29. 

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