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Bembenek BM, Petersen MMS, Lilly JA, Haugen AL, Jiter NJ, Johnson AJ, Ripp EE, Winchell SA, Harvat AN, McNulty C, Thein SA, Grieger AM, Lyle BJ, Mraz GL, Stitgen AM, Foss S, Schmid ML, Scanlon JD, Willoughby PH. The Aryne-Abramov Reaction as a 1,2-Benzdiyne Platform for the Generation and Solvent-Dependent Trapping of 3-Phosphonyl Benzynes. J Org Chem 2021; 86:10724-10746. [PMID: 34236859 DOI: 10.1021/acs.joc.1c01382] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Synthetic methodology utilizing two aryne intermediates (i.e., a formal benzdiyne) enables the rapid generation of structurally complex molecules with diverse functionality. This report describes the sequential generation of two ortho-benzyne intermediates for the synthesis of 2,3-disubstituted aryl phosphonates. Aryl phosphonates have proven useful in medicinal chemistry and materials science, and the reported methodology provides a two-step route to functionally dense variants by way of 3-phosphonyl benzyne intermediates. The process begins with regioselective trapping of a 3-trifloxybenzyne intermediate by an O-silyl phosphite in an Abramov-like reaction to bond the strained Csp carbons with phosphorus and silicon. Standard aryne-generating conditions follow to convert the resulting 2-silylphenyl triflate into a 3-phosphonyl benzyne, which readily reacts with numerous aryne trapping reactants to form a variety of 2,3-difunctionalized aryl phosphonate products. DFT computational studies shed light on important mechanistic details and revealed that 3-phosphonyl benzynes are highly polarizable. Specifically, the distortion in the internal bond angles at each of the Csp atoms was strongly influenced by both the electronegativity of the phosphonate ester groups as well as the dielectric of the computational solvation model. These effects were verified experimentally as the regioselectivity of benzyl azide trapping increased with more electronegative esters and/or increasingly polar solvents. Conversely, replacing the conventional solvent, acetonitrile, with nonpolar alternatives provided attenuated or even inverted selectivities. Overall, these studies showcase new reactivity of benzyne intermediates and extend the aryne relay methodology to include organophosphonates. Furthermore, this work demonstrates that the regioselectivity of aryne trapping reactions could be tuned by simply changing the solvent.
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Affiliation(s)
- Brianna M Bembenek
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Maya M S Petersen
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Julia A Lilly
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Amber L Haugen
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Naomi J Jiter
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Andrew J Johnson
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Ethan E Ripp
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Shelby A Winchell
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Alisha N Harvat
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Caitlin McNulty
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Sierra A Thein
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Abbigail M Grieger
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Brandon J Lyle
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Gabriella L Mraz
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Abigail M Stitgen
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Samuel Foss
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Merranda L Schmid
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Joseph D Scanlon
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
| | - Patrick H Willoughby
- Chemistry Department, Ripon College, 300 West Seward Street, Ripon, Wisconsin 54971, United States
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