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

   https://doi.org/10.1055/s-0039-1690869  

   Abdul-Rashed, Shukree; Holt, Connor; Frontier, Alison J. (July 2020, Synthesis)

   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 Introduction 1.1 Alkyne-Carbonyl Coupling Pathways 1.2 Coupling/Cyclization Cascades Using the Alkynyl Prins Reaction 2 Alkynyl Prins Annulation (Oxocarbenium Electrophiles) 2.1 Early Work 2.2 Halide as Terminal Nucleophile 2.3 Oxygen as Terminal Nucleophile 2.4 Arene as Terminal Nucleophile (Intermolecular) 2.5 Arene Terminal Nucleophile (Intramolecular) 2.6 Cyclizations Terminated by Elimination 3 Synthetic Utility of Alkynyl Prins Annulation 3.1 Alkynyl Prins-Mediated Synthesis of Dienes for a [4+2] Cyclo­- addition­-Oxidation Sequence 3.2 Alkynyl Prins Cyclization Adducts as Nazarov Cyclization Precursors 3.3 Alkynyl Prins Cyclization in Natural Product Synthesis 4 Alkynyl Aza-Prins Annulation 4.1 Iminium Electrophiles 4.2 Activated Iminium Electrophiles 5 Alkynyl Aza-Prins Cyclizations in Natural Product Synthesis 6 Summary and Outlook 

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2. Alkynyl Halo-Aza-Prins Annulative Couplings

   https://doi.org/10.1021/acs.joc.3c01305  

   Hernandez, Jackson J; Lawrie, Alexandra P; Frontier, Alison J (December 2023, The Journal of Organic Chemistry)
3. P-Alkynyl functionalized benzazaphospholes as transmetalating agents

   https://doi.org/10.1039/d0dt01367f  

   Zhou, Daniel Y.; Miura-Akagi, Preston M.; McCarty, Sierra M.; Guiles, Celeste H.; O'Donnell, Timothy J.; Yoshida, Wesley Y.; Krause, Colleen E.; Rheingold, Arnold L.; Hughes, Russell P.; Cain, Matthew F. (January 2021, Dalton Transactions)

   null (Ed.)

   Exposure of 10π-electron benzazaphosphole 1 to HCl, followed by nucleophilic substitution with the Grignard reagent BrMgCCPh afforded alkynyl functionalized 3 featuring an exocyclic –CC–Ph group with an elongated P–C bond (1.7932(19) Å). Stoichiometric experiments revealed that treatment of trans -Pd(PEt 3 ) 2 (Ar)( i ) (Ar = p -Me ( C ) or p -F ( D )) with 3 generated trans -Pd(PEt 3 ) 2 (Ar)(CCPh) (Ar = p -Me ( E ) or p -F ( F )), 5 , which is the result of ligand exchange between P–I byproduct 4 and C/D , and the reductively eliminated product (Ar–CC–Ph). Cyclic voltammetry studies showed and independent investigations confirmed 4 is also susceptible to redox processes including bimetallic oxidative addition to Pd(0) to give Pd( i ) dimer 6-Pd2-(P(t-Bu)3)2 and reduction to diphosphine 7 . During catalysis, we hypothesized that this unwanted reactivity could be circumvented by employing a source of fluoride as an additive. This was demonstrated by conducting a Sonogashira-type reaction between 1-iodotoluene and 3 in the presence of 10 mol% Na 2 PdCl 4 , 20 mol% P( t -Bu)Cy 2 , and 5 equiv. of tetramethylammonium fluoride (TMAF), resulting in turnover and the isolation of Ph–CC–( o -Tol) as the major product. 

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4. Tandem Bond-Forming Reactions of 1-Alkynyl Ethers

   https://doi.org/10.1021/acs.accounts.6b00107  

   Minehan, Thomas G. (June 2016, Accounts of Chemical Research)
5. One‐Pot Transition‐Metal‐Free Synthesis of Alkynyl Amides

   https://doi.org/10.1002/anie.202415472  

   Wu, Yu; Sátiro, Bárbara G; Mao, Jianyou; Walsh, Patrick J (January 2025, Angewandte Chemie International Edition)

   Abstract Alkynyl amides play crucial roles in organic synthesis in the production of bioactive compounds and valuable heterocycles. Despite numerous studies on their synthesis, challenges persist due to the necessity of harsh or hazardous conditions and the use of costly or unstable reagents. Herein, we present a one‐pot method for the synthesis of all three bonds of the alkyne under transition‐metal‐free conditions. An important feature of this chemistry is the use of readily available feedstock chemicals, such as methyl esters and acetamides. This approach offers efficient access to a wide range of aryl and alkyl alkynyl amides and demonstrates excellent tolerance towards various functional groups in a sustainable and cost‐effective manner. 

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