Pyrroles, 2-cyclopropyl

An analogous cyclization to eventually form five-membered rings has also been observed for l-metalla-l,3,5-hexatrienes with an additional heteroatom within the chain, such as in the complexes 157. These are obtained by Michael additions of imines to alkynylcarbene complexes in good to excellent yields (reaction type F in Scheme 4), and their configurations were determined to be Z (>91%) in all cases. Upon warming in THF solution, complexes 157 underwent cyclization with reductive elimination to furnish 2Ff-pyrroles 158 in up to 97% yield (Scheme 34). With two cyclopropyl substituents at the terminus in... 

Replacement of the ethanolamine head group is also well tolerated. Substitution with a cyclopropyl (243) [37], allyl (244) or propargyl group (245) [164] all led to an increase in binding affinity compared to AEA. Replacement of the head group with aromatics is also allowed. The phenyl derivative (246) retains affinity at the CBi receptor [37], whereas the 2-substituted A-methyl pyrrole (247) has a 2-fold improved affinity compared to AEA [167]. Interestingly, the 3-substituted furan derivative (23) that has micromolar affinity for the AEA transporter (see above) does not bind to the CBi receptor, but has good affinity for the CB2 receptor [167]. These results are summarised in Table 6.20. 

Das ziemlich einfach herstellbare 1 -Hydroxy- 1-piperidino-cyclopropan kann in Gegen-wart von Titan(IV)-chlorid in einer Variante der Mannich-Reaktion als Aquivalent von Cyclopropanon/Piperidin dienen nach der anzunehmenden in-situ-Umwandlung in 1-Cyclopropyliden-piperidinium-chlorid erfolgen Reaktionen z.B. mit 1-Trimethylsiloxy-cyclohexen zu 2-Oxo-l-(l-piperidino-cyclopropyl)-cyclohexan (63%) und mit 1-Methyl-pyrrol bzw. Indol zu l-Methyl-2-( 1-piperidino-cyclopropyl)-pyrrol (65%) bzw. 3-(l-Pipe-ridino-cyclopropyl)-indol (84%)2 ... 

Representatives of Alkenyl and Cyclopropyl Pyrroles Derived from Alkenyl and Cyclopropyl Ketoximes... 

The reason for the particular ease of formation of 1, l-di-(2-cyclopropyl-5-pyrryl)ethane (98a) evidently consists in the high electron-donor ability of cyclopropyl, which increases the pyrrole ring nucleophilicity. 

This condensation helps one understand why the yield of pyrroles from ketoximes and acetylene is reduced in some cases and consequently allows a more directed search for ways to overcome this obstacle. Optimization of this side reaction would make possible a one-pot preparation of valuable dipyrroles with cyclopropyl or vinyl substituents, such as 98a,c for example. 

H-Pyrrol 2-(3-Pyridyl)-4,5-dihydro- (Miosmin) El4b. 269 [aus Cyclopropyl-imino-methyl)-pyridin]... 

No cyclopropane-like product ions, i.e. cyclopropyl cyanide ion (7), were generated from various pyridine precursors. By using collisional activation it was shown that 4-hydroxy-or 4-aminopyridines (129) dissociate via loss of CO or HCN, respectively, to form 3H-pyrrole (130), whereas CO loss from ionized 2-hydroxy pyridine (131) gives rise to the formation of IH-pyrrole (10). In other cases, mixtures of 2H- and either IH- or 3H-pyrroles are generated, depending on the nature of the precursor (Scheme 20). 

The formation of pyrroles by the reaction of the cyclopropylketimine (63) with HBF4 has been studied from a mechanistic point of view using 3-chloropropionyl chloride enriched with at the carbonyl carbon atom The C-NMR spectrum of the pyrrole formed from the cyclopropyl ketimine (63) shows enhancement of the peak at the 5-carbon in accord with mechanism A outlined in Scheme 27. Operation of process B analogous to the vinylcyclopropane rearrangement 63a would have led to enrichment at the 3-carbon of the pyrrole product. 

Z)-3-(aminomethyl)-4-(methoxyimino)-1 -pyrrol idiny I]-1 -cyclopropyl-6-fluoro-1,4-dihydro -4-oxo-1,8-naphthyridine-3-carboxylic acid... 

Cyclopropyl Isocyanates from 3,4-Dihydro-2 f-pyrrol-2-ones... 

With an imino substituent at the alkenyl terminus, a, -unsaturated pentacarbonyl(car-bene)chromium complexes 30 did not insert alkynes, but cyclized directly, even with cyclopropyl substituents present, to give 2//-pyrroles 31 in high yield. ... 

It should be noted that condensation of pyrrole and chiral cyclopropyl derivatives affords the isomer of/ttc.vo-... 

Catalytic Synthesis of Dimethyl 3-Cyclopropyl-1 H-pyrrole-2,4-dicarboxylate... 

Molecular ions of cyclopropyl cyanide, allyl cyanide, methacrylonitrile, and pyrrole rearrange to one common radical ion, most likely that of pyrrole [4]. 

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