Z-Butoxide

Reinhoudt, Gray, Smit and Veenstra prepared a number of monomer and dimer crowns based on a variety of substituted xylylene units. They first conducted the reaction of 1,2-dibromomethylbenzene and a polyethylene glycol with sodium hydride or potassium Z-butoxide in toluene solution. Mixtures of the 1 1 and 2 2 (monomer and dimer) products were isolated and some polymer was formed . The reaction was conducted at temperatures from 30—60° and appeared to be complete in a maximum of one hour. The authors noted that the highest yield of 1 1 cyclic product was obtained with disodium tetraethylene glycolate instead of dipotassium hexaethylene gly-colate (see also Chap. 2) . Chloromethylation of 1,3-benzodioxole followed by reaction with disodium tetraethylene glycolate afforded the macrocycle (29% yield) illustrated in Eq. (3.20). 

Spiroorthocarbonates were obtained by coupling of cyclic tin adduct 251, prepared from 1,2-dihydroxymethyl-benzene and dibutyltin oxide, with thiocarbonate 252. Reaction of the resulting orthocarbonate 253 with potassium A/z-butoxide in toluene afforded spiroorthocarbonate 254 (Scheme 77) <2003BKC1371>. 

A solution of 5-trimethylsilyldecan-4-one (lmmol) in THF (5 ml) was treated withMeLi (3 mmol, 0.85 Min ether) at -78°C with stirring, and the mixture was stirred at ambient temperature overnight. Potassium t-butoxide (9mmol) was added, and the mixture heated under reflux for 1 h, to give, after work-up, the alkenes as a 91 9 mixture of ( ) (Z) isomers, in 74% yield. 

Simple acetylenic allylic alcohols can be cyclized easily by tarf-butoxide, and since this base initiates prototropic shifts the vinylic link may.be E or Z such cyclizations proceed via exomethylene furans similar to 15.65 If necessary, UV irradiation can effect both the isomerization of an to a Z-alkene and the cyclization, leaving only the final adjustments to be made chemically.66 In a variation, methoxide plays the role of leaving group allowing very good yields to be attained (Scheme 10).67... 

Bicyclo[2.2.1]hepten-7-one has been prepared by the oxidation of (z-7-hydroxybicyclo[2.2. ljheptene with chromic acid in acetone 2 and with aluminum t-butoxide in benzene with benzoqui-none as the hydrogen acceptor.3 The procedure described here is essentially that of Gassman and Pape.4... 

Fig. 2.1.9. Mass chromatograms (m/z 58) of alkylbenzyldimethylammonium chlorides as their corresponding alkyldimethylamines and the internal standard (undecyldimethyl-amine) (a) prior to debenzylation and (b) after Hofmann degradation with potassium tert-butoxide and El mass spectra detected in river water. Reproduced with permission from Ref. [141]. 2001 by American Chemical Society.

Treatment of 7-chloroamine 363 with potassium /i t/-butoxide in refluxing THE gave rise to a mixture of (Z-tert-butyl)-5,5-dimethyl-5,6-dihydro-4f/-l,3-oxazine 366 and 1-pivaloylazetidine 367 (Scheme 67). The heterocycles 366 and 367 were formed through generation of the Favorskii intermediate 364 by dehydrocyanation, which was followed by opening of the cyclopropylideneamine by /r-rt-butoxide with the subsequent loss of isobutene and a subsequent intramolecular N-alkylation or O-alkylation of the amide anion 365 <1999EJ0239>. 

We have further examined the effect of initiators and solvents on the equilibrium product distribution. The use of lithium tert-butoxide instead of potassium tert-butoxide and the change of solvent from THF to toluene showed no effect on the product distribution of e-caprolactone oligomers.4 Also we are examining the equilibrium oligomer distribution in cationic system such as trifluoromethane sulfonic acid catalyst.z... 

R. The use of butyllithium in tetrahydrofuran or ether-hexane affords the triene 1n only 50-60% yield. When the ylide was generated with sodium hydride or potassium tert-butoxide in dimethyl sulfoxide by the submitter, the Wittig reaction gave triene containing 10-20% of the Z isomer. Part C illustrates the selective hydroboration of a diene with disiamylborane.1 The reaction is best carried out by adding preformed disiamylborane to the triene. Lower yields of homogeraniol were obtained by the submitter when the triene was added to the borane reagent. 

Difluorododecanes 29 with potassium rerr-butoxide in tetrahydrofuran eliminate hydrogen fluoride stereoselectivcly the meso and syn compounds give, respectively, (E)- and (Z)-6-fluorododec-6-ene (30).26... 

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

Bromination of 8 followed by dehydrobromination afforded completely unsaturated compound 10. Barium hydroxide and zinc reduction of 10 yielded 11 (69JOC3237). ( >1,2-Diazacyclooctene 12 (R1 - R4 = Me) was synthesized by oxidative cyclization of 2,7-dimethyl-2,7-octanediamine with iodine pentafluoride (78CB596). [For preparation of the stereoi-someric Z compounds, see Section II,A,3,a.] Stetterand Koch reacted bis(Af-bromoamino)biadamantyl 13 with potassium terf-butoxide and isolated a molecule containing a 1,2-diazocine sandwiched between two ada-mantane moieties (14) [see also Section II,A,3,c] (75LA1357). 

Also, reaction of 2-phenyl-6-methylbenzo[6]furan with Schiff s base derived from 2-phenyl-6-formylbenzo [Z>]furan and p-chloroaniline (47) in the presence of potassium t-butoxide gives 1,2-di(2-phenylbenzo[6]-furan-6-yl)ethylene (48).37... 

The double dehydrobromination of oc,a -dibromoalkanedicarboxylates (5) is a good route to cycloalkene diesters when n = 2-4, but unfortunately is not successful with n = 1 when (5, n = 1) is treated with one equivalent of potassium t-butoxide, a reasonable yield of the E- and Z-bromides (6, X = Br) is obtained, but a second equivalent of base leads to E- (6, X = BulO), presumably by addition of t-butylalcohol,... 

The treatment of alkynyliodonium salts not amenable to cyclopentene formation with sodium azide in methanol affords vinyliodonium salts and/or enol ethers (equation 107)". Enol ether formation also occurs when glyme is employed as the solvent (equation 108)". Finally, regeneration of the vinylidene-iodonium ylide, PhC (N3)=C—IPh, from (Z)-(/ -azido-/ -phenylvinyl)phenyliodonium tosylate with potassium J-butoxide in glyme likewise affords an enol ether (equation 109). 

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