Bases, cyclopropyl-substituted

Reaction of 2,3-dichloroquinoxaline 367 with sodium azide in ethanol has been used to synthesize bistetrazolo-[l,5- 5, l -c]quinoxaline 368 in 65% yield (Scheme 28) <1997JOC4082>. Similarly, reaction of 2,3-dichloroquinoxaline 367 with thiosemicarbazide 366 has been used to generate l,6-diamino-bis-l,2,4-triazolo[4,3- 3,4-f]quinoxaline 365 in 67% yield <2002AP389>. Condensation of cyclopropanecarboxylic acid hydrazide 369 meanwhile gives rise to the cyclopropyl-substituted tetracycle 370 in 93% yield in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base (Scheme 28) <2005JOC2878>. 

An index for predicting the reaction course of intramolecular photochemical cyclization of cycloheptatrienes and tropones, based upon the LCAO coefficients at the reaction sites of the HOMO S and LUMO s of the excited states, has been developed. The n.m.r. spectrum of the 8,9-benzobicyclo[5,2,0]nonatetraenyl anion (118) shows the presence of bond fixation and a preference for the dimethyl-enecyclobutene form. ° The rates of one-electron reduction of cyclopropyl-substituted tropylium perchlorates by chromous ion are consistent with the cyclopropyl group preferring a bisected conformation. ... 

Cyclopropyl-substituted imidazopyridine is afforded in 55% isolated yield upon stirring in, V-dimethylformamide at 95 C for 1.5 h. The catalytic inorganic base is critical to the reaction yield as shown by the optimization of the reaction conditions... 

Metal-mediated [5 -I- 2] cyclizations were built based on the hypothesis that the cyclopropyl moiety of cyclopropyl substituted enynes might participate in the rearrangement process as a three atom unit. This approach afforded indeed an efficient process for the formation of 7-membered rings starting from enynes with a cyclopropyl moiety on the olefin terminus [51]. A possible mechanistic model involves coordination of the enyne and oxidative coupling (a), followed by cleavage of the cyclopropyl unit (b) and reductive elimination (Fig. 10.38). 

Inhibition mechanisms by A/-cyclopropyl MPTP analogues are also discussed in terms of two catalytic pathways, one of which is based on an initial SET step from the nitrogen lone pair, as proposed by Silverman, and the second is based on an initial a-carbon hydrogen atom transfer (HAT) step, as proposed by Edmondson, leading to a radical and dihydropyridinium product formation. The observation that MAO B catalyzes the efficient oxidation of certain 1-cyclopropyl-4-substituted-1,2,3,6-tetrahydropyridines to the corresponding dihydropyridinium metabolites suggests that the catalytic pathway for these cyclic tertiary allylamines may not proceed via the putative SET-generated aminyl radical cations [122], Further studies will be necessary to clarify all the facets of the mechanism of inhibition of MAO by cyclopropylamines. 

As discussed above, many cyclopropylamines are good inhibitors of MAOs. In addition, as discussed in Section 3.2, fluorine substitution had substantial effects on the inhibition of MAOs by such analogues as allylamines. We undertook a broadly based study of the effects of fluorine substituted on the cyclopropyl ring of cyclopropyl amines on potency and selectivity of amine oxidase inhibition. In addition to effects on amine pKg and lipophilicity, we expected additional consequences resulting from altered geometry and ring strain due to the presence of fluorine. 

Active methylene and methine compounds bearing a leaving group (X) on the y-carbon atom can afford cyclopropyl derivatives via 1,3-elimination of HX. 1,2-Elimination to give alkenes and direct nucleophilic substitution by base may compete with the 1,3-elimination, particularly in the preparation of excessively strained cyclopropyl derivatives. The preferred reaction course is, however, highly dependent on reaction conditions, especially on the nature of the base and solvent employed, as exemplified by the reactions of 4 (equation 7) 4. 

As demonstrated below, a Lewis acid-mediated reaction was utilized in the synthesis of dihydro[b furan-based chromen-2-one derivatives from l-cyclopropyl-2-arylethanones and allenic esters <070L4017>. The TiCh-catalyzed anti-Markovnikov hydration of alkynes, followed by a copper-catalyzed O-arylation was applied to the synthesis of 2-substituted benzo[6]furan <07JOC6149>. In addition, benzo[6]furan-based heterocycles could be made from chloromethylcoumarins <07SL1951>, substituted cyclopropanes <07AGE1726>, as well as benzyne and styrene oxide <07SL1308>. On the other hand, DBU-mediated dehydroiodination of 2-iodomethyl-2,3-dihydrobenzo[6]furans was also useful in the synthesis of 2-methylbenzo[Z>]furans <07TL6628>. 

Most attempts to design narcotic antagonists based on 4-phenylpiperidine by linking the basic center to groups such as allyl, substituted allyl, and cyclopropyl methyl (CPM) that confer such properties on fused cyclic systems as possessed by morphine and 6,7-benzomorphans have led to agonists that have no power to block opiate receptors examples include TV-allyl derivatives of norpethidine and norprodine (18)34 and the TV-3-chloroallyl reversed ester 19.(56) Essentially similar results were found for a group of TV-substituted... 

C yclopropyl ketones. Substituted cyclopropyl ketones can be obtained by base-induced isomerization of y, -epoxy ketones. Thus treatment of the epoxide (2) of... 

In order to enhance the acid lability of ferf-butyl esters, several derivatives have been proposed based on the substitution of one or more methyl groups by residues which increase the stability of the intermediate tertiary carbocation in acidolytic deprotection. Phenyl, cyclopropyl, and adamantyl substituents have been used for such purposes. 

Cyclobutanols substituted by a leaving group at the 2-position are transformed into cyclopropanecarbaldehydes or cyclopropyl ketones upon treatment with base . The reaction of a 3,4-dichlorocyclobutene derivative with aqueous base to give a 2-cyclopropen-l-yl ketone probably proceeds via a 4-chlorocyclobut-2-en-l-ol (equation 104) 67 jjj oxidation of 1-methylcyclobutene with metallic salts in aqueous medium to... 

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