Eliminations potassium ferf-butoxide

Nucleophilic displacement of bromide from 5-acetyl-10-bromo-5//-dibenz[7>,/]azepine (41) by alkoxide,132 and by cyanide ion in dimethylformamide,212 has been noted. However, replacement of bromide by cycloalkylamines (e.g., piperidine) to give the 10-cycloalkylamino derivatives. e.g. 44, is best accomplished in the presence of potassium ferf-butoxide, a result which suggests that the aminodebromination proceeds via an elimination-addition (EA) pathway involving an azepyne intermediate 43 (see Section 3.2.1.5.7.) rather than by the more usual addition-elimination (AF.) mechanism.118... 

Compounds A and B are isomers of molecular formula C9H19Br. Both yield the same alkene C as the exclusive product of elimination on being treated with potassium ferf-butoxide in dimethyl sulfoxide. Hydrogenation of alkene C gives 2,3,3,4-tetramethylpentane. What are the structures of compounds A and B and alkene C ... 

If, however, the base itself is a crowded one, such as potassium ferf-butoxide, even primary alkyl halides undergo elimination rather than substitution ... 

Another example of based-catalyzed elimination in the 2-deoxy sugar series is that of l-[2-deoxy-3-0-(methylsulfonyl)-5-0-trityl-/3-D-eryMro-pentofuranosyl]uracil and 2, 3-anhydro-l-(2-deoxy-5- 0-trityl-/3-D-<. reo-pentofuranosyl) uracil, which, when treated with potassium ferf-butoxide in methyl sulfoxide, give a 70% yield of a 2,3-unsaturated nucleoside.28... 

Elimination of hydrogen chloride from 1,1-dichloromethyl sulfide with potassium ferf-butoxide affords chloromethylthiocarbene [3] (equation 5)... 

Exercise 8-26 a. Why is potassium ferf-butoxide, KOC(CH3)3, an excellent base for promoting elimination reactions of alkyl halides, whereas ethylamine, CH3CH2NH2, is relatively poor for the same purpose ... 

Explain why (lS,3i )-3-ferf-butylcyclohexyl tosylate undergoes E2 elimination with potassium ferf-butoxide very slowly while the (1 A ,3 A ) reacts much more rapidly. 

Dichlorocarbene cannot be isolated, but it can be produced in the presence of an alkene with which it rapidly reacts. The best dichlorocarbene precursor is the anion C13C , which easily eliminates a chloride ion. This anion is obtained from C13CH and fairly strong bases like potassium ferf-butoxide (KO-ferf-Bu), KOH or NaOH. The deprotonation of C13CH is run very efficiently with a solution of KO-terf-Bu in THF. Alternatively, when a concentrated aqueous solution of NaOH or KOH is vigorously stirred with a chloroform solution of the alkene (which is not miscible with the first) there is only moderate conversion into the corre-... 

Allylic bromides 383 and 384 were the relais substances for the synthesis of coriamyrtin (9) (Scheme 43). The allylic bromides were eliminated with potassium ferf-butoxide in toluene affording diene 387. 1,4-Addition with W-bromosuccini-mide in polar solvent at room temperature yielded the unsaturated a-bromo-5-hydroxy unit of 388, which formed the unsaturated epoxide 389 by base treatment. Epoxidation with peracid occurred as expected from the convex face. The cyclic ether moiety of bisepoxide 390 was oxidized to the lactone 368 with ruthenium... 

In extension of our silver(l)-mediated synthesis of pyrroles, we have developed a catalytic version which could be realized by using a tosyl function as acceptor at the nitrogen atom. Thus, cyclization of A-tosyl-substituted homopropargylamines 12 to A -pyrrolines 13 has been achieved with catalytic amounts of the silver(l) salt. Aromatization by subsequent elimination of p-toluenesulfinic acid on treatment with potassium ferf-butoxide as base afforded the pyrroles 14 (Scheme 4) [31]. 

Aziridines. With the vast array of literature available on epoxides, it is surprising that the base-promoted elimination of aziridines is almost unknown in the literature. One of the earliest examples using sodium alkoxides in refluxing alcoholic solvents was reported in 1989 by Stamm and Speth. Scheffold reported an aziridine to allylamine conversion in 1993 using a cob(I)alamin catalyst. Recently, Mordini and co-workers demonstrated the use of a LDA/potassium ferf-butoxide mixture (pentane, room... 

The most often applied and most reliable procedure to obtain a cycloalkyne (Fig. 2, bottom), as originally developed by Brandsma in the Netherlands, [11], involves the stepwise double dehydrohalogenation of a vicinal dihalogenide (typically bromide), which can be readily obtained from a cyclic alkene upon treatment with elemental halogen. In this case, a first E2-elimination may take place under mildly basic conditions, forming an intermediate alkene, which in turn will undergo a second elimination upon treatment with a strong base like sodium amide or potassium ferf-butoxide. More conveniently even, in many cases both... 

On the basis of this palladium-mediated Michael addition cyclization process, a novel two-step synthetic entry into functionalized furan derivatives 67 has also been devised (Scheme 28). Substitution of benzylidene (or alkyli-dene) malonates for their ethoxymethylene analog (65) as activating olefins gave rise to the formation of the corresponding 2-ethoxy-4-arylidene tetrahy-drofurans 66. An in situ addition of potassium ferf-butoxide induced a decar-boxylative elimination reaction which was followed by an isomerization of the exocychc double bond. The entire process successively involved a conjugate addition, a palladium-catalyzed cycHzation-coupling reaction, a base-induced eliminative decarboxylation, and finally, a double bond isomerization (73). 

Compound A (CgHi4) gives three different monochlorides on photochemical chlorination. One of these monochlorides is inert to E2 elimination. The other two monochlorides yield the same alkene B (CgHi2) on being heated with potassium terf-butoxide in ferf-butyl alcohol. Identify compound A, the three monochlorides, and alkene B. 

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