ChemInform Abstract: The “tert.-Amino Effect” in Heterocyclic Chemistry: Synthesis of 3,1-Benzoxazines and 3,1-Benzothiazines (original) (raw)
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6-Iodo-2-isopropyl-4H-3,1-benzoxazin-4-one as building block in heterocyclic synthesis
Synthetic Communications, 2016
As a part of ongoing studies in the synthesis of a variety of heterocycles of biological importance, we report here an efficient and convenient method for the synthesis of novel compounds from 6iodo-2-isopropyl-4H-3,1-benzoxazin-4-one 1 as building block. The reaction of benzoxazinone 1 with various reagents such as diethylmalonate, sodium azide, and phosphorus pentasulfide yielded the compounds 2-5. The behavior of benzothiazin-4-thione 5 toward formamide and hydrazine hydrate was investigated, forming the compounds 6 and 7. The reaction of quinazolinone derivative 8 with β-D-glucose pentaacetate, ethyl 2-methyl-5-((1S,2R,3R)-1,2,3,4-tetrahydroxybutyl)furan-3-carboxylate, epichlorohydrin and benzenesulphonyl chloride afforded quinazolinone derivatives 9, 10, 12, and 13 respectively. The reaction of quinazolinone derivative 10 with acetic anhydride resulted in formation of the acylated compound 11. The behavior of quinazolinylacetohydrazide derivative 14 toward carbon electrophiles [16] has been investigated by its reaction with ethyl benzoylacetate, potassium thiocyanate, and phenyl isothiocyanate, affording the quinazolinone derivatives 15, 16, and 18, respectively. Treatment of compound 16 with sodium hydroxide followed by hydrochloric acid yielded the mercapto-triazole derivative 17. The structures of the newly synthesized compounds were confirmed by elemental analysis, infrared (IR), 1 H NMR, 13 C NMR, and mass spectra. The antimicrobial activities of some of the synthesized compounds were preliminarily evaluated.
Synthesis of isoquinolines by cycloaddition of arynes to 1,2,4-triazines
Tetrahedron, 1992
Benxyne has been generated from benzencdiezonimn-2carboxylate in the presence of several 1,2,4triaxinea 1 snd isoquinolines 2 have been is&ted ia inodeam yield. I-Aminobenarkole was also used as the scurce of benxyne and kxpinolines went again is&ted in mode&e yield from these react&s CMe&ykuyne, which was generated from 5-methybhranilic acid, reacted unselectively with the trkines to give mixtmes of d and 7-methylisaquinolines 3 and 4 On the ok hand reactions of 3-methylbenzyne with the hiazines Id aid le promded with high regioselectivity, giving only the 5-methylisoquiaoline Sa and the Il-meUtytkoquinoline 6h. respectively. 1,2,4-Triazines are well established as heterodienes in the Diels-Alder reaction; them are many examples of both intermolecular and intramolecular cycloadditions, in which the triazines normally act as the electron deficient reaction partners.1 We have investigated the cycloaddition reactions of several 1,2&triazines with benzyne in order to evaluate the method as a route to isoquinolines. Benzyne is known to undergo cycloaddition to several types of cyclic heterodiene including 1,2,4,5-tetrazines 2 and oxazoles 3. The reaction with oxazoles results in the formation of isoquinolines as byproducts. Benzyne has also been shown to react with N-benzylideneaniline to give a formal cycloadduct, 5,6-dihydro-5.6-diphenylphenanthridine, in low yield.4 However, we wished to prepare isoquinolines with electron withdrawing substituents in the nitrogen containing ring, particularly isoquinoline-I-carboxylic esters bearing additional substituents, which are not readily available by existing routes.5 Reucrions with Benzyne. A series of 1 ,2,4-triazines 1 was prepared by standard methods. Benzenediazonium-2-carboxylate was first used as the source of benzyne. Each of the triazines was dissolved in dioxan, the solution was heated under reflux, and dioxan solutions of anthranilic acid (in threefold excess) and isoamyl nitrite were added simultaneously to the solution over a period of about 20 min. The products were isolated by flash column chromatography. From each of the triazines la to lf a cycloadduct 2 was isolated (Scheme 1). The yields were moderate, ranging from 13% starting from the chlorotriazine la to 56% starting from the ttiazinecarboxylic ester le. The isoquinolines 2 (none of which has been prepared before) were fully character&d. A characteristic feature of the tH NMR spectra is a low field doublet for 8-H (Table) and this feature subsequently proved useful in assigning structures to adducts from methylbenzynes.
Tetrahedron, 1988
The partly saturated 1,3-benzoxazino[3,4-a][3,l]benzoxazine (2) and 1,3_benzoxaeino[3,2-c][l,3]benzoxazines (gp-2) were prepared in one-pot syntheses from trans-2-hydroxymethylcyclohexylamine (2) and trans-2-aminomethylcyclohexanol (5) via ring-chain tautomEric mixtures. IH nmr spectroscopic cha<actF ization of the products Ga-q, including the assignment of the resulting diastereomers IS presented.
Synthesis of 1-[4-(1,5-DIALKYL-1H-1,2,4-TRIAZOL-3-YL)]BENZYL-1H-INDOLES and 5,6-DIHALOQUINOLONES
Organic Preparations and Procedures International, 2002
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