Indolizine synthesis

Benzimidazolo[l,2-c]thiatri azoles synthesis, 6, 612 Benz[cd]indazole antiaromaticity, 5, 208 Benz[cd]indazole, dihydroaromaticity, 5, 208 Benz[e]indolizine synthesis, 4, 466 Benzipiperylon biological activity, 5, 296 Benz[/]isoindoles synthesis, 4, 266... 

A major advantage of this indolizine synthesis is that the procedures are generally very simple and the process requires two steps at the most. Since the reactivities of 1,3-dipoles as well as dipolarophiles are sensitive to electronic and steric influences, the substituents in the 1-, 2- and 3-positions of the indolizine nucleus are restricted mostly to electron withdrawing and relatively small groups. If unsymmetric dipolarophiles have almost similar groups in polar and steric character at both ends of the reaction center, a mixture of the two possible isomers is often obtained. 

Pyrrolo[l, 2-a]imidazoI-2(3 ff)-ones synthesis, 6, 1001 Pyrrolo[3,2-6]indoles synthesis, 4, 243 Pyrrolo[3,2-/]indolizines synthesis, 4, 274, 296 Pyrroloisoquinolines synthesis, 4, 513... 

The base-induced cyclization of Ar-(oxoethyl(pyridinium salts of 2-picolines, known as the Tschitschibabin indolizine synthesis, is a classical method of preparation of indolizines from pyridines. The ready isolation of the products by decanting or filtration has allowed for the recent development of a parallel synthesis of a wide range of 2-substituted indolizines <2003SL2086>. 

Indolizines, synthesis of via ketene dithio acetals 85YGK669. 

Indolizines, synthesis via ketene dithio acetals 85YGK669. Naphthimidazopyridinediones, synthesis and quaternization of 79SOC34. Naphthindolizinediones, synthesis, quaternization, properties as dyes and... 

This procedure parallels the classical indolizine synthesis <69CB669>. A 2-methyl cycloiminium ion provides the four-membered chain which is joined to the five-membered ring by condensation with phosphorus trichloride <955361 >. 

Indolizine synthesis by reaction of pyridinyl ketones with aldehydes in the presence of ammonium acetate, (see 1st edition). 

The first example of a stable pyridinium yhde of type 80 is the pyridinium phenacylide (80, A = CH2COPh), obtained from the N-phenacylpyridinium ion (79, A = CH2COPh) by deprotonation with Na2C03 [97]- The reactivity of the pyridinium betaines is determined by their electron distribution (80a-c). Thus, they can be smoothly alkylated or acylated at the N-substituent ( 81) as 1,3-dipoles, they undergo dipolar cycloadditions with activated alkynes or alkenes [98] for example, the sequence 80 —> 82 83 establishes an efficient principle of indolizine synthesis (cf. p. 154). 

In the Scholtz indolizine synthesis 2-picoline is heated with acetic anhydride, giving diacetylindolizine. The reaction has been represented as going by diacetylation of the methyl groups... 

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