Heterocyclic Chemistry at a Glance
Pyridines 45 group and the fi rst step is the displacement of pyrrolidine by the ammonia, via addition/elimination, ring closure ...
46 Pyridines formal aldol condensation, and the 1,6-bond in a formal enamine formation, though the precise order of events is no ...
Pyridines 47 Exercises What factors make it much more diffi cult to bring about electrophilic substitution of pyridine than ben ...
Heterocyclic Chemistry at a Glance, Second Edition. John A. Joule and Keith Mills. © 2013 John Wiley & Sons, Ltd. Published ...
Diazines 49 Unlike the purines, these pyrimidine bases and their nucleosides and nucleotides generally do not have a great deal ...
50 Diazines The amino-diazines, benefi ting from activation by the electron-releasing substituent, generally undergo electrophil ...
Diazines 51 Substitution of leaving groups The nucleophilic displacement of halogen and other leaving groups by ‘soft’ nucleophi ...
52 Diazines Radical substitution The Minisci reaction (page 14) is particularly useful in the diazines because there are many si ...
Diazines 53 Lithiodiazines are also accessible via halogen exchange with alkyllithiums. The examples show how 5-bromopyrimidine ...
54 Diazines Negishi cross-couplings with organozinc reagents and Stille reactions with stannanes, prepared by various means, hav ...
Diazines 55 Mesoionic pyrazinium-3-olates undergo cycloadditions similar to those known for pyridinium-3-olates (page 40) and py ...
56 Diazines N-Alkylation of O-silylated derivatives is an important method for unambiguous N-alkylation, especially for ribosyla ...
Diazines 57 N-Oxides(see also page 49) Nucleophilic displacement of nitro at C-3 in pyridazine N-oxides (i.e. to an N-oxide fu ...
58 Diazines Diazine diazonium salts are even less stable than those in the pyridine series and are only synthetically useful for ...
Diazines 59 With regard to the 1,3-dicarbonyl unit, when a carbonyl is at the acid/ester oxidation level, oxygenated pyrimidines ...
60 Diazines ‘pteridine’ – the pteridine ring system is present in a number of important natural products (pages 159–160). Pterid ...
Diazines 61 Exercises How could one convert an oxydiazine, where the oxygen is to a nitrogen, into (i) a corresponding chloro ...
7. Quinolines and Isoquinolines Heterocyclic Chemistry at a Glance, Second Edition. John A. Joule and Keith Mills. © 2013 John W ...
Quinolines and Isoquinolines 63 Exceptionally, and via a different mechanism, some substitutions in the pyridine ring of quinoli ...
64 Quinolines and Isoquinolines stabilisation is lost in proceeding to the intermediate (strictly, the transition state which le ...
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