Potassium tert -butoxide

As illustrated in eq 5, a./S-unsaturated ketones undergo a,a-dialkylation when treated with excess r-BuOK/f-BuOH and an alkylating agent4 The K.a-dimethylated, y-unsaturated ketone is formed by conversion of the initially produced a-methylated /3,y-unsaturated ketone to its dienolate, which undergoes a second methylation faster than the 8, /-double bond is isomerized to the a,/3-position.  

In contrast to intermolecular processes, intramolecular alkylations are frequently performed with f-BuOK in various solvents. In eqs 6 and 7 are shown examples of endo- and exo-cycloalkylations of cyclic saturated ketones which lead to new five-membered rings.  

An interesting example of how a change in the base can influence the course of a cycloalkylation reaction is shown in eq 8. Since the reaction with f-BuOK involves equilibrating conditions, exo-cycloalkylation occurs via the more-substituted eno-late, which is more thermodynamically stable. On the other hand, when LDA is used as the base, endo-cycloalkylation occurs via the kinetically formed terminal enolate. 

Intramolecular alkylations of Q ,/3-unsaturated ketones may occur at the a-, a -, or y-positions depending upon the nature of the base, the leaving group, and other structural features. A recent example involving a-cycloalkylation using f-BuOK is shown in eq 9.  

The reaction of a-halo esters, ketones, nitriles, and related compounds with appropriate organoboranes in the presence of f-BuOK can lead to replacement of the halogen with an alkyl or an aryl group. An example of this reaction using an a-bromD ester 

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This isomerization, which must proceed through a 1,2,3-trienylanine, is not "contra-thermodynamic", since with a catalytic amount of potassium tert.-butoxide the same result is obtained. Enyne ethers, H2C=CH-CsC-0R, undergo a similar conversion into HCeC-CH=CH-OR upon interaction with alkali metal amides in liquid NH3, followed by hydrolysis . Enyne sulphides, H2C=CH-CsC-SR, and the hydrocarbons H2C=CH-CsC-R (R = or phenyl) give only tars or polymeric products under... 

Similarly sodium methoxide (NaOCHj) is a suitable base and is used m methyl alco hoi Potassium hydroxide m ethyl alcohol is another base-solvent combination often employed m the dehydrohalogenation of alkyl halides Potassium tert butoxide [K0C(CH3)3] is the preferred base when the alkyl halide is primary it is used m either tert butyl alcohol or dimethyl sulfoxide as solvent... 

Use curved arrows to show the bonding changes in the reaction of CIS 4 tert butylcyclohexyl bromide with potassium tert butoxide Be sure your drawing correctly represents the spatial relationship between the leaving group and the proton that is lost... 

Compound A (C4H10) gives two different monochlondes on photochemical chlorination Treatment of either of these monochlondes with potassium tert butoxide in dimethyl sulfoxide gives the same alkene B (CaHg) as the only product What are the structures of compound A the two monochlondes and alkene B2... 

Compound A (CgHi4) gives three different monochlondes on photochemical chlonnation One of these monochlondes is inert to E2 elimination The other two monochlondes yield the same alkene B (CgHi2) on being heated with potassium tert butoxide in tert butyl alcohol Men tify compound A the three monochlondes and alkene B... 

Compounds A and B are isomers of molecular formula C9Hi9Br Both yield the same alkene C as the exclusive product of elimination on being treated with potassium tert 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 C2... 

If however the base itself is a crowded one such as potassium tert butoxide even pn mary alkyl halides undergo elimination rather than substitution... 

Double dehydrohalogenation to form terminal alkynes may also be carried out by heating geminal and vicinal dihalides with potassium tert butoxide m dimethyl sulfoxide... 

Dihalocarbenes are formed when trihalomethanes are treated with a strong base such as potassium tert butoxide The trihalomethyl anion produced on proton abstraction dissociates to a dihalocarbene and a halide anion... 

Potassium tert butoxide reacts with halobenzenes on heating in dimethyl sulfoxide to give ten butyl phenyl ether... 

Difluorododecane is unaffected by sodium methoxide in methanol, but its treatment with potassium tert-butoxide in tetrahydrofuran eliminates hydrogen fluonde stereospecifically rneso and dl compounds give, respectively, ( )- and (2) 6 fluoro 6 dodecene [12] (equation 11)... 

The dichloride 8.21a forms fragile, lamellar crystals with a golden colour. The X-ray structure reveals a layered arrangement of hexameric units formed by linking three ( BuNTeCl2)2 dimers by chloride bridges. The reaction of 8.21a with potassium tert-butoxide yields... 

The reaction of phthalaldehyde and diethyl oxydiacetate in the presence of potassium tert-butoxide gives, with hydrolysis of the ester function, 3-benzoxepin-2,4-dicarboxylic acid (2a).89 The reaction of the dimethyl ester lb gives dimethyl 3-benzoxepin-2,4-dicarboxylate (2 b) when... 

Hydrogen bromide is eliminated from 10,11-dibromo-l 0,1 l-dihydrodibenz[7>,/]oxepin with potassium tert-butoxide at room temperature to give 10-bromodibenz[i,/]oxepin (17a).160161 When the elimination reaction was performed in boiling toy-butanol the yield increased from 58 to 92%.261 Dehydrohalogenation of 10-chloro-2,3-dimethoxy-10,ll-dihydrodi-benz[/),/]oxepin afforded 2,3-dimethoxydibenz[6,/]oxepin (17b) in 52% yield.162... 

The ketones 1 and 3, or compounds with a similar structure, have been used for the preparation of methoxy derivatives of 1-benzoxepin. In the standard procedure for methylation, the 1-benzoxepinone is deprotonated by potassium tert-butoxide and subsequently reacted with methyl fluorosulfonate at low temperature.16 173 - 175 The yields are generally high. 

The first synthesis of a 3//-3-benzazepine, e.g. 65 (R1 = R2 = Me), was achieved by the condensation of phthalaldehyde with a bis[(alkoxycarbonyl)methyl]methylamine.24"25 With sodium methoxide as the base, A%V-bis[(methoxycarbonyl)methyl]pheiiylaniine condenses with the dialdehyde in a similar manner to give dimethyl 3-phenyl-3//-3-benzazepine-2,4-dicar-boxy late (65, Rl — Ph R2 — Me).99 However, replacement of methoxide by potassium tert-butoxide results in formation of 3-phenyl-3//-3-benzazepine-2,4-dicarboxylic acid (65, R1 = Ph R2 = H).25... 

Additionally, the sulfonamide precursor to 75 could be recovered and recycled to regenerate the bromoborane 75 [36], The resulting aldols could then be cyclized to the epoxy esters by treatment with potassium tert-butoxide (Scheme 1.22). 

Chelation of the enolate and orientation of the acceptor chain away from the chclatc, seems to be essential as the use of potassium tert-butoxide in to / -butyl alcohol (nonchelated enolate) results in a 1 1 mixture of cis- and tram-2132-I33. The diastereomeric ratio furthermore depends on the alcohol (R20) moiety134- 136-386, whereas the use of zirconium(IV) isopropoxide also results in high tram-selectivity (cisjtrans ratio, 1 25) 137. 

Based on the use of 2 (R1 = H), metalated with two equivalents of potassium tert-butoxide in tetrahydrofuran, routes to (S)-phosphinotricin (79% ee) and glutamic acid (69% ee) were developed211. 

Various chiral crown ethers based on [1,1 -binaphthalene]-2.2 -diol, lactose or other chiral 1,2-di-ols were tested as catalyst in the addition of methyl benzcneacetate to methyl 2-propenoate using sodium amide or potassium tert-butoxide as the base. Some pertinent examples are given261 262 396. 

Potassium tert-butoxide from a freshly opened bottle supplied by the MSA Research Corporation was used. 

Treatment either of pure isomers or of a mixture consisting of 22-24 with potassium-tert-butoxide provided 22 in high yield (eqn. 2). 

Trialkylboranes react rapidly and in high yields with a-halo ketones,a-halo esters, a-halo nitriles, and a-halo sulfonyl derivatives (sulfones, sulfonic esters, sulfonamides) in the presence of a base to give, respectively, alkylated ketones, esters, nitriles, and sulfonyl derivatives. Potassium tert-butoxide is often a suitable base, but potassium 2,6-di-tert-butylphenoxide at 0°C in THF gives better results in most cases, possibly because the large bulk of the two tert-buXy groups prevents the base from coordinating with the R3B. The trialkylboranes are prepared by treatment of 3 mol of an alkene with 1 mol of BH3 (15-16). With appropriate boranes, the R group transferred to a-halo ketones, nitriles, and esters can be vinylic, or (for a-halo ketones and esters) aryl. " °... 

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