Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

Abstract

SummaryVarious N-propargylpyrrole and indolecarboxylic acids were efficiently converted into 3,4-dihydropyrrolo- and indolo-oxazin-1-one derivatives by a gold(III)-catalyzed cyclization reaction. Some of the products underwent TFA-catalyzed double bond isomerization and some did not. Cyclization reactions in the presence of alcohol catalyzed by Au(I) resulted in the formation of hemiacetals after cascade reactions.

Nucleophilic and electrophilic cyclization of N-alkyne-substituted pyrrole derivatives: Synthesis of pyrrolopyrazinone, pyrrolotriazinone, and pyrrolooxazinone moieties

“…The reaction of 8 with NaOMe in methanol gave pyrrole ester 9 (Scheme 1) [19,24]. It is essential to use bromoalkynes for N -alkyne substitution of pyrrole ester 9 .…”

Base‐Promoted Formation of an Annelated Pyrrolo‐1,4‐oxazine Ensemble from 1H‐pyrrol‐2‐ylmethanol and Propargyl Chloride: A Theoretical and Experimental Study

“…To the best of our knowledge, in the literature there are only a few reports on construction of the pyrrole-and indoleoxazine ensembles, which, however, contain a keto group in the oxazine fragment. [21,22] Such ensembles are obtained by cyclization of the corresponding pyrrole-or indole-2-carboxylic acids and their ethers functionalized with alkynyl moieties at the nitrogen atom. It should be emphasized that the triple bond at the nitrogen atom can be either conjugated with pyrrole or separated by a methylene group.…”

“…Regioselectivity of addition to a carbon atom at the triple bond is controlled by selecting the appropriate catalyst (copper or gold-containing one). [21,22] The preparation of similar structures via sophisticated iodine-or iron-catalyzed assemblies (domino reactions) from exotic building blocks has been reported. [23,24] Also known is the formation of indolyloxazines through complex gold-catalyzed cascade assembly based on functionalized acetylene alcohols.…”

Synthesis and Reactivity of Oxazinoindolones via Regioselective 6‐exo‐dig Iodolactonization

“…Synthetic methods for access to this kind of structure include lactonization from the ester or acid indoles, [7] transesterification, [3,8] Friedel-Crafts alkylation, [9] cyclodehydration from the free-NH indole, [10] aza-Michael addition, [11] copper catalyzed cyclization, [12] hydroamination [13] of the acid system and more recently by gold catalyzed cyclization of the carboxylic acid. [14] In contrast to these, the construction of oxazinoindolones by iodolactonization is rare. To the best of our knowledge, there is only one report by B. Joseph et al which described a system with NIS and 2,6-lutidine at -20 °C allowing the formation of iodo-oxazinoindolone.…”