Alkyl and alkenyl groups

A-Alkyl groups in neutral azoles can rearrange thermally to carbon. For example, 2-alkylimidazoles can be prepared in this way in a reaction which is irreversible, uncatalyzed, intramolecular and does not involve radicals (80AHC(27)24l). 

1-Methylbenzotriazole is lithiated readily with n-BuLi or LDA at the methyl group and the subsequent reactions with various electrophiles provide 1-substituted benzotriazoles. Other 1-(n-alkyljbenzotriazoles also undergo lithiation with LDA (94LAi). 2-Alkylbenzotriazoles behave 

The benzotriazole moiety of iV-(a-aminoalkyl)benzotriazoles is readily replaced by hydride upon reduction with sodium borohydride, or with a carbanion by reaction with Grignard or lithium reagents. These are two of the most important reactions of benzotriazole derivatives from which versatile routes have been developed for the synthesis of primary, secondary, and tertiary amines. 

Reactivity of Five-membered Rings with Two or More Heteroatoms 

Additions to /V-alkeny I imidazoles are influenced by conjugation with the heteroring (Equation 9) a vinyl group is not cleaved when l-vinyl-3-alkyl quaternary salts are thermolyzed and 1-vinylimidazole is not subject to thermal rearrangement (80AHC(27)24t, 82CHEH90,84JHC133). 

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Organocopper reagents. Dialkenyl tellurides are readily transformed into copper reagents for conjugate addition, on reaction with CuCN-RLi. When the tellurides contain both alkyl and alkenyl groups they are also transformed into alkenylcuprates. 

R2 is hydrogen, C g alkyl or C g alkenyl wherein said alkyl and alkenyl groups are optionally substituted with halo ... 

Ion series Most fragments are halogenated alkyl and alkenyl groups, easily detectable on the basis of the isotope signals in the cases of Cl and Br. 

By use of trialkylaluminums a range of alkyl and alkenyl groups can be introduced at C-1 compound 44 can be obtained in 72% yield by treatment of di-0-acetyl-6-deoxy-D-galactal in dichloromethane at -78°C with trimethylalumi-num in the presence of titanium tetrachloride (Scheme 15) [62], and the doubly C-1-substituted 45, required for natural product synthesis, is produced stereo-specifically from tri-O-acetyl-l-C-allyl-D-glucal by a similar methylation procedure [63]. 

Some ants make products reminiscent of the coccinellid alkaloids. Three indolizidines are known from the venom gland of Monomorium pharaonis (Figure 9.10), and a pyrrolizidine from a Solenopsis ant has been known for some time. They would appear to be formed from polyketides or fatty acids as in the case of the coccinellines. More pyr-rolizidines and indolizidines with two alkyl and alkenyl groups have been found in Monomorium and Solenopsis species. Tetraponerine ants smear the venom of their poison glands onto prey. The venom consists of tricyclic alkaloids called tetraponerines (Figure 9.10). They are divided... 

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