Reaction of benzothiazole and substituted benzothiazoles with dimethyl acetylenedicarboxylate. A novel heterocyclic ring transformation

Abstract

Reaction of benzothiazole with dimethyl acetylenedicarboxylate in aqueous methanol gives irons-dimethyl 4formyl-2,3-dihydro-l,4-benzothiazine-2,3-dicarboxylate in high yield, and a mechanism is proposed for this novel transformation. The scope and limitations of the process have been defined by examination of the reactions of a wide range of substituted benzothiazoles with dimethyl acetylenedicarboxylate in aqueous methanol; the results are fully consistent with the postulated mechanism.

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

“…In fact, for now, four approaches to BTAs III are known [21][22][23][24][25] (Scheme 2). They include the reaction of dimethyl acetylenedicarboxylate (DMAD) with o-aminothiophenol (1a) on the catalyst SiO 2 @H 3 PW 12 O 40 [21], the reaction of tetracarbonyl compounds with o-aminothiophenol (1a) [22,23], the Scheme 1: Reported structure A of assayed compound [9] and its correct structure B.…”

“…reaction of copper(II) chelate of ethyl pentafluorobenzoylpyruvate with o-aminothiophenol (1a, one example) [24] and the reaction of DMAD with 6-nitro-1,3-benzothiazole (one example) [25]. Our recent research [26] revealed that the approach based on the reaction of tetracarbonyl compounds with o-aminothiophenol (1a) [22,23] is a mistaken one.…”

“…In fact, for now, four approaches to BTAs III are known [ 21 – 25 ] ( Scheme 2 ). They include the reaction of dimethyl acetylenedicarboxylate (DMAD) with o -aminothiophenol ( 1a) on the catalyst SiO 2 @H 3 PW 12 O 40 [ 21 ], the reaction of tetracarbonyl compounds with o -aminothiophenol ( 1a ) [ 22 – 23 ], the reaction of copper(II) chelate of ethyl pentafluorobenzoylpyruvate with o -aminothiophenol ( 1a , one example) [ 24 ] and the reaction of DMAD with 6-nitro-1,3-benzothiazole (one example) [ 25 ]. Our recent research [ 26 ] revealed that the approach based on the reaction of tetracarbonyl compounds with o -aminothiophenol ( 1a ) [ 22 – 23 ] is a mistaken one.…”

An efficient synthesis of 2H-1,4-benzoxazin-3(4H)-ones via Smiles rearrangement

“…10 Despite their importance from pharmacological, industrial, and synthetic point of view, comparatively few methods for their preparation were reported. Some of the methods reported in the literature for the synthesis of oxazine derivatives are McKillop cycloaddition, 11 N-and O-alkylation with dibromo compounds, 12 lithiation method, 13 use of chiral epoxides under phase transfer catalysts. 14 However, very few methods are available for the synthesis of 1,4-benzoxazinone or 1,4-pyridooxazinone derivatives.…”

Συνθεση Και Μελετη Συμπυκνωμενων Κουμαρινο-Ετεροκυκλικων Συστηματων

“…τολουόλιο,139 . Η μονοξίμη(121) δεν αντέδρασε κατά τη θέρμανση της σε τολουόλιο, ενώ κατά την επίδραση του ημισταθερού υλιδίου (47) έδωσε το αντίστοιχο οζαζολικό παράγωγο (122) 139 . R 122 Κατά την αντίδραση της (111) με το υλϊδιο Ph 3 P=CHCOCH 3 (68) ελήφθη μίγμα πολλών προϊόντων σε μικρές αποδόσεις και μη διαχωριζομένων 136 .…”