N-CHLORO-2,3,4,4,5,6-HEXACHLOROCYCLOHEXA- 2,5-DIENYLIDENEAMINE AS A MILD AND HIGHLY REGIOSELECTIVE CHLORINATING REAGENT
4
Citation
15
Reference
10
Related Paper
Abstract:
ABSTRACT N-Chloro-2,3,4,4,5,6-hexachlorocyclohexa-2,5-dienylideneamine was used as a new, mild and highly regioselective chlorinating reagent in the chlorination of phenol and o-cresol in CCl4, DMF and CH3CN. The effects of C2H5OH, C5H5N, DMF and Et3N on the regioselectivity in CCl4 have also been examined.β-Aminoenones react with monoalkyl hydrazines to give regioselectively 1,3,5-trisubstituted pyrazoles. The mechanism and level of regioselectivity depend on both the substitution pattern of the substrates and the reaction conditions. When the least bulky substituent is attached at the β-position of the enone, a high regioselectivity is obtained, usually higher than that from equivalent β-diketones. If the β-substituent is the bulkiest group, the regioselectivity decreases. Nevertheless, in the conditions reported in this paper, it is possible to prepare pyrazoles not obtainable from β-diketones.
Enone
Cite
Citations (12)
Abstract The alkynes (IIa) or (IIb) react almost regioselectively or with poor regioselectivity with the pyrones (I), (V) and (VIII), while the reaction of both with the pyrone (XI) is regioselective.
Pyrone
Diels–Alder reaction
Cite
Citations (0)
Cite
Citations (1)
Pauson–Khand reaction
Cite
Citations (19)
Pyrazole is the ubiquitous sub-structure of many natural products and biologically active compounds. In this respect, its regioselective synthesis drew a lot of attention from synthetic organic chemists, leading to the development of various regioselective modifications of the classical Knorr cyclocondensation reaction and alternative methods. This review covers the period of 2003 to the middle of 2009 on the regioselective synthesis of pyrazoles, which are categorized into four reaction types: (i) modified Knorr condensation reaction using 1,3-dicarbonyl surrogates; (ii) 1,3-dipolar cycloadditions approach; (iii) regioselective direct substitution reaction of the pyrazole ring system; and (iv) other methods. Keywords: Pyrazole, regioselective dipolar cycloaddition, regioselective condensation, regioselective cross-coupling
Pyrazole
Cite
Citations (68)
Abstract A perfectly regioselective and sequential method for the preparation of orthogonally protected glucopyranosides has been developed. An acyl group was introduced at C(4)‐OH by organocatalysis with >99 % regioselectivity. TBDPS, Boc, and BOM groups were sequentially introduced into the 4‐ O ‐acyl‐glucopyranoside at C(6)‐OH, C(2)‐OH, and C(3)‐OH, respectively, with ca. 100 % regioselectivity in each step.
Cite
Citations (50)
The regioselectivity of the Suzuki couplings of several 4,5- and 3,4-dibromopyrrole-2-carboxylate esters has been studied. In general, regioselectivity can be achieved for initial coupling at the more electron-deficient site (C5 and C3, respectively). At the same time, conversions are often modest (40-60%) and attempts to force the reactions to higher conversions often lead to competitive dicoupling.
Carboxylate
Suzuki reaction
Cite
Citations (19)
Mitsunobu reaction
Solid-Phase Synthesis
Cite
Citations (53)
ABSTRACT N-Chloro-2,3,4,4,5,6-hexachlorocyclohexa-2,5-dienylideneamine was used as a new, mild and highly regioselective chlorinating reagent in the chlorination of phenol and o-cresol in CCl4, DMF and CH3CN. The effects of C2H5OH, C5H5N, DMF and Et3N on the regioselectivity in CCl4 have also been examined.
Cite
Citations (4)