- Large-scale solvent-free chlorination of hydroxy-pyrimidines,-pyridines,- pyrazines and-amides using equimolar POCl3
-
Chlorination with equimolar POCl3 can be efficiently achieved not only for hydroxypyrimidines, but also for many other substrates such as 2-hydroxy-pyridines,-quinoxalines, or even-amides. The procedure is solvent-free and involves heating in a sealed reactor at high temperatures using one equivalent of pyridine as base. It is suitable for large scale (multigram) batch preparations.
- Wang, Han,Wen, Kun,Wang, Le,Xiang, Ye,Xu, Xiaocheng,Shen, Yongjia,Sun, Zhihua
-
experimental part
p. 4533 - 4544
(2012/06/30)
-
- Synthesis of polyhalogenated 4,4′-bipyridines via a simple dimerization procedure
-
Polyhalogenated 4,4′-bipyridines were conveniently synthesized in a single step starting from dihalopyridines. A mechanism was proposed on the basis of experiments performed with 2-chloro-5-bromopyridine 1a. 2-Chloro-4-lithio-5- bromopyridine A1 was produced via ortholithiation of 1a by using either LDA or t-BuLi bases. When LDA was used, dimer 3a containing two chlorines and two bromine atoms was formed predominantly accompanied by several byproducts whose structure and mechanism of formation are discussed. In the case of t-BuLi, although the major product was 2-chloropyridine 7, a new pyridone product 8 was formed that is probably the result of the dihydropyridine intermediate hydrolysis. The dimerization procedure involving LDA was employed to prepare a large number of halogenated 4,4′-bipyridines in moderate to good yields. In some specific cases, halogenated 3,4′ and 2,4′-bipyridines were obtained in lower yields and their structures were unambiguously assigned by X-ray diffraction analysis.
- Abboud, Mohamed,Mamane, Victor,Aubert, Emmanuel,Lecomte, Claude,Fort, Yves
-
scheme or table
p. 3224 - 3231
(2010/08/19)
-
- Stereoselective synthesis of conformationally constrained tropane analogues: 6-Chloro-2,5-diazatetracyclo[8.5.0.02,13.0 4,9]pentadeca-4,6,8-triene-11-one and 6-chloro-2,7-diazatetracyclo- [8.5.0.02,13.04,9]pentadeca-4,6,8-triene-11-one
-
Two conformationally constrained tropane derivatives were prepared as rigid nicotinic acetylcholine receptor ligands. A palladium catalyzed intramolecular α-arylation reaction was employed to generate the tricyclic compounds in good yields from N-(bromo-chloropyridylmethyl)-8-azabicyclo[3.2.1]octan-3-ones.
- Cheng, Jie,Xu, Liang,Stevens, Edwin D.,Trudell, Mark L.,Izenwasser, Sari,Wade, Dean
-
p. 569 - 574
(2007/10/03)
-
- Unusual t-BuLi induced ortholithiation versus halogen-lithium exchange in bromopyridines: Two alternative strategies for functionalization
-
The reaction of lithiating agents with various 3-bromopyridines has been investigated. An unprecedented selectivity was observed with t-BuLi, which effected a clean lithiation at C-4. With 3-bromo and 2-chloro-3-bromo pyridines, the ortholithiation-exchange ratio was strongly electrophile and addition order dependent while 2-chloro-5-bromopyridine always gave exclusive C-4 substitution.
- Pierrat, Philippe,Gros, Philippe,Fort, Yves
-
p. 2319 - 2322
(2007/10/03)
-