Halide-Terminated <i>N</i>-Acyliminium Ion−Alkyne Cyclizations:  A New Construction of Carbacephem Antibiotics

Metais, E.; Overman, Larry E.; Rodriguez, María Inés; Stearns, Brian A.

doi:10.1021/jo971433w

Cited by 44 publications

(27 citation statements)

References 25 publications

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“…The resulting residue was purified by silica gel chromatography (20:1 hexanes-EtOAc) to afford tetrahydrofurans 13b and 12b (26 mg, 96%) as a 92:8 mixture 3 . The major stereoisomer 13b was separated by preparative MPLC (silica gel, 20:1 hexanes-EtOAc): 1…”

Section: Rearrangement Of Acetals With Sncl 4 Preparation Of Rel-(2mentioning

confidence: 99%

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Stereoselection in the Prins-Pinacol Synthesis of Acyltetrahydrofurans

et al. 2001

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A. Representative Experimental Procedures 1 Preparation of r e l-(2S,4R,5S)-4-Ethenyl-4,5-dimethyl-2-isopropyl-1,3-dioxolane (6a).A solution of a 6:1 mixture of anti-and syn-3-methyl-4-penten-2,3-diols 2 (820 mg, 7.10 mmol), isobutyraldehyde (2.5 g, 35 mmol), MgSO 4 (15 g), CH 2 Cl 2 (140 mL), and p-TSOH (130 mg, 0.68 mmol) was stirred at rt for 4 h before being poured into saturated aqueous NH 4 Cl (50 mL). The resulting layers were separated and the aqueous layer was extracted with CH 2 Cl 2 (2 × 100 mL). The combined organic layers were dried (MgSO 4 ), filtered, and concentrated. The residue was purified by silica gel chromatography (20:1 hexanes-EtOAc) to give a 6:1 mixture of acetals 6a and 6s (900 mg, 74%) as a colorless oil. The major stereoisomer 6a was separated by preparative MPLC (silica gel, 100:1 hexanes-EtOAc): 1 H NMR (500 MHz, CDCl 3 ) δ 5.75 (dd, J = 10.7, 11.1 Hz, 1H), 5.23 (dd, J = 15.9, 1.6 Hz, 1H), 5.13 (dd, J = 9.1, 1.6 Hz, 1H), 4.70 5, 114.2, 106.3, 81.5, 81.3, 32.1, 22.5, 17.2, 17.1, 15.4; IR (film) 3015, 2977 IR (film) 3015, , 2933 IR (film) 3015, , 2874 IR (film) 3015, , 1473 IR (film) 3015, , 1412 IR (film) 3015, , 1384 IR (film) 3015, , 1108 IR (film) 3015, , 1006 Am. Chem. Soc. 1991, 113, 5354-65.

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Section: Rearrangement Of Acetals With Sncl 4 Preparation Of Rel-(2mentioning

confidence: 99%

“…The combined organic layers were dried (MgSO 4 ), filtered, and concentrated. The resulting residue was purified by silica gel chromatography (20:1 hexanes-EtOAc) to give 12a (15 mg, 90%) as a single diastereomer 3 : 1…”

Section: Rearrangement Of Acetals With Trifluoromethanesulfonic Acidmentioning

confidence: 99%

Stereoselection in the Prins-Pinacol Synthesis of Acyltetrahydrofurans

et al. 2001

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“…The Overman group employed a halide-terminated Nacyliminium cyclization as the key step in their synthesis of functionalized carbacephem antibiotics (Scheme 29). 55 Remarkably, the reaction proceeds in 60% yield under Lewis acidic conditions, despite the presence of additional functional groups in the substrate. The aza-Prins adduct 130 was then converted into the target carbacephem antibiotics in only three additional steps.…”

Section: Reviewmentioning

confidence: 96%

Alkynyl Prins and Alkynyl Aza-Prins Annulations: Scope and Synthetic Applications

Abdul-Rashed¹,

Holt²,

Frontier³

2020

Synthesis

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This review focuses on alkynyl Prins and alkynyl aza-Prins cyclization processes, which involve intramolecular coupling of an alkyne with either an oxocarbenium or iminium electrophile. The oxocarbenium or iminium species can be generated through condensation- or elimination-type processes, to achieve an overall bimolecular annulation that enables the synthesis of both oxygen- and nitrogen-containing saturated heterocycles with different ring sizes and substitution patterns. Also discussed are cascade processes in which alkynyl Prins heterocyclic adducts react to trigger subsequent pericyclic reactions, including [4+2] cycloadditions and Nazarov electrocyclizations, to rapidly construct complex small molecules. Finally, examples of the use of alkynyl Prins and alkynyl aza-Prins reactions in the synthesis of natural products are described. The review covers the literature through the end of 2019.1 Introduction1.1 Alkyne-Carbonyl Coupling Pathways1.2 Coupling/Cyclization Cascades Using the Alkynyl Prins Reaction2 Alkynyl Prins Annulation (Oxocarbenium Electrophiles)2.1 Early Work2.2 Halide as Terminal Nucleophile2.3 Oxygen as Terminal Nucleophile2.4 Arene as Terminal Nucleophile (Intermolecular)2.5 Arene Terminal Nucleophile (Intramolecular)2.6 Cyclizations Terminated by Elimination3 Synthetic Utility of Alkynyl Prins Annulation3.1 Alkynyl Prins-Mediated Synthesis of Dienes for a [4+2] Cyclo- addition-Oxidation Sequence3.2 Alkynyl Prins Cyclization Adducts as Nazarov Cyclization Precursors3.3 Alkynyl Prins Cyclization in Natural Product Synthesis4 Alkynyl Aza-Prins Annulation4.1 Iminium Electrophiles4.2 Activated Iminium Electrophiles5 Alkynyl Aza-Prins Cyclizations in Natural Product Synthesis6 Summary and Outlook

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“…After several unsuccessful attempts, [8] the chlorovinyl structure in rac-4 was finally oxidized by means of ruthenium(VIII) oxide [9] according to the protocol of Overman et al [10] The hydroxypyranone rac-5 was obtained in 67% yield (Scheme 3). The relative configuration at C-6 of rac-5 was determined by NOESY experiments, showing distinctive NOE enhancements between 2-H and 6-H.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Heptano Bridged Pyranoside Derivatives

Kirsch¹,

Wolff²,

Näther³

et al. 2000

Eur. J. Org. Chem.

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Addition of dichlorocarbene to the glycal (±±)‐2 followed by cyclopropyl‐allyl rearrangement leads to the chloro‐2H‐pyran (±±)‐4. Oxidation of (±±)‐4 and reduction of the obtained hydroxypyranone (±±)‐5 gave the methyl pyranoside (±±)‐6. The relative configuration of (±±)‐6 was established by X‐ray structural analysis of the corresponding acetate (±±)‐7. The synthesis of the optically active starting materials (+)‐2 and (−)‐2 is also reported.

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Halide-Terminated N-Acyliminium Ion−Alkyne Cyclizations: A New Construction of Carbacephem Antibiotics

Cited by 44 publications

References 25 publications

Stereoselection in the Prins-Pinacol Synthesis of Acyltetrahydrofurans

Stereoselection in the Prins-Pinacol Synthesis of Acyltetrahydrofurans

Alkynyl Prins and Alkynyl Aza-Prins Annulations: Scope and Synthetic Applications

Synthesis of Heptano Bridged Pyranoside Derivatives

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