A Novel [3+2] Cycloaddition Approach to Nitrogen Heterocycles via Phosphine-Catalyzed Reactions of 2,3-Butadienoates or 2-Butynoates and Dimethyl Acetylenedicarboxylate with Imines:  A Convenient Synthesis of Pentabromopseudilin

Abstract

The reactivity of a new three carbon synthon, generated in situ from the reaction of 2,3-butadienoates or 2-butynoates with an appropriate phosphine as the catalyst, toward the electron-deficient imines is described. Triphenylphosphine-catalyzed reaction of methyl 2,3-butadienoate with N-sulfonylimines gave the single [3+2] cycloadduct in excellent yield; tributylphosphine-catalyzed reaction of methyl 2,3-butadienoate or 2-butynoate with N-tosylimines afforded the corresponding [3+2] cycloadduct as the major product along with a small amount of the three components adduct. Aliphatic N-tosylimines gave moderate yield for this reaction. In addition, a new phosphine-catalyzed cyclization reaction of dimethyl acetylenedicarboxylate with N-tosylimines is also described. A reaction mechanism is proposed. Further elaborations of the cycloaddition products and the synthesis of pentabromopseudilin using this method are exemplified.

Nucleophilic Phosphine Organocatalysis

“…[66] Kwon and coworkers envisioned that substitution of the hydrogen at the a-position of the 2,3-butadienoate with an alkyl group might block a-attack of the phosphonium intermediate and lead to a reaction manifold initiated by g-addition. Remarkably, mixing 2-alkyl-2,3-butadienoate derivatives with N-tosylbenzaldimines in the presence of 20 mol % PBu 3 [Eq.…”

Biosynthesis of the Marine Antibiotic Pentabromopseudilin. 2. The Pyrrole Ring

“…8) Its structure has been elucidated by X-ray crystallography and confirmed by three independent syntheses. [9][10][11] The biosynthesis of violacein (2) has been elucidated, and it was shown that it is derived from tryptophan. 12) Two structural features of 1 are unusual: the straightforward carbon framework and its extremely high content of bromine (over 70%) combined with high biological activity.…”

Phosphine‐mediated Highly Enantioselective Spirocyclization with Ketimines as Substrates

“…Ketimines derived from awide range of isatin structures were all well tolerated, regardless of the electronic nature and substitution pattern of the aryl moieties of the ketimines.I n all the cases examined, 3,2'-pyrrolidinyl spirooxindoles were produced in good yields and with 99 %ee (Table 2, entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Furthermore,the reaction could be repeated on alarger scale ( Table 2, entry 15).…”

“…[1] Nitrogen-containing ring systems are prevalent molecular architectures that are widely found in natural products and are extremely valuable as synthetic intermediates.Phosphine-catalyzed allene-imine annulation [2] is one of the most powerful methods for constructing such motifs,a nd has been widely employed in numerous syntheses of natural products and bioactive molecules. [3] In the vast majority of reported examples,aldehydederived aldimines are the electrophilic reaction partners utilized in these reactions.K etimines,o nt he other hand, are seldom used.…”