2,1-Benzothiazine 2,2-Dioxides. 5*. Hydrolysis of Alkyl 1-R-4-Hydroxy-2,2-Dioxo-1Н-2λ6,1-Benzo-Thiazine-3-Carboxylates**

Updating the CSIC Reaction (2003–2020)

“…CSICr described by Mascarenhas et al [59] Scheme 21. CSICr reported by Ukrainets et al [49,50] Scheme 22. CSICr described by Carroll et al [60] by acid hydrolysis.…”

“…[35] Entry NH-CSICr precursor The synthesis of diversely substituted 1H-benzo[c][1,2] thiazin-4(3H)-one 2,2-dioxides III (Figure 2) follows a well and simple three-step protocol proposed by Lombardino in the seventies, [44] consisting of the CSICr of a N-alkyl-N-(methylsulfonyl)anthranilate, obtained from the reaction of an anthranilate and methanesulfonyl chloride, followed by Nalkylation of the resulting intermediate. This procedure has been used later by other authors without significant modifications, under conventional conditions [43,[45][46][47][48][49][50][51][52][53][54][55][56] or solid-phase, a very appropriate method for the combinatorial synthesis of heterocyclic compound libraries, albeit in low chemical yields. [57] Scheme 15.…”

“…Ukrainets and colleagues have been very active on the synthesis of highly functionalized sultams [49,50] In their first communication, [49] and as shown in Scheme 21, the authors reported the synthesis of diversely substituted and functionalized alkyl 2-((N-alkyl(allyl, phenyl)-2-alkyloxy-2-oxoethyl) Scheme 17. CSICr described by Manfroni et al [45] Scheme 18.…”

“…CSICr described by Sokolov et al [58] Scheme 19. Double intramolecular CSICr described by Sokolov et al [58] In a subsequent paper published by the same group, [50] the hydrolysis of 4-hydroxy-1-alkyl(allyl,phenyl)-1H-benzo[c][1,2] thiazine-3-carboxylate 2,2-dioxides 94 has been explored in detail. As shown in Scheme 21, the reaction of compounds 94 in strong acidic conditions (HCl/AcOH) produced the hydrolysis plus decarboxylation products 95 a-e, the same result that was observed when molecules 94 were treated with aqueous potassium hydroxide, at reflux, for a short time (20 min).…”

“…Ukrainets and colleagues have been very active on the synthesis of highly functionalized sultams [49,50] In their first communication, [49] and as shown in Scheme 21, the authors reported the synthesis of diversely substituted and functionalized alkyl 2‐(( N ‐alkyl(allyl, phenyl)‐2‐alkyloxy‐2‐oxoethyl)sulfonamido)benzoates 93 by N ‐acylation of methyl anthranilates 92 a – e with commercially available alkyl chlorosulfonylacetates 40 a – c , in CH 2 Cl 2 , in the presence of triethylamine (Et 3 N). Next, the intramolecular CSICr was carried by reacting compounds 93 with R 3 ONa/R 3 OH (R 3 =Et, Me), in mild reaction conditions, to give the expected alkyl 4‐hydroxy‐1‐alkyl(allyl,phenyl)‐1 H ‐benzo[ c ][1,2]thiazine‐3‐carboxylate 2,2‐dioxides 94 in good yields (77‐94 %).…”