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Abstract A practical protocol for the first regiodivergent asymmetric addition of aryl and alkenyl organometallic reagents to substitutedN‐alkyl pyridinium heterocycles is described. The couplings proceed with high regiochemical and stereochemical selectivities, and provide access to chiral 1,2,3‐ and 1,3,4‐trisubstituted dihydropyridine products, controlled by judicious choice of nitrogen activating agent. To this end, a correlation was found between the parameterized size of the activating group and the C2/C4 regioselectivity in the couplings. The utility of the described chemistry was demonstrated in two concise asymmetric syntheses of (+)‐N‐methylaspidospermidine and (−)‐paroxetine.
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Intramolecular Pyridinium Oxide Cycloadditions: Systematic Study of Substitution, Diastereoselectivity, and Regioselectivity
Abstract Intramolecular pyridinium oxide cycloadditions form complex polycyclic nitrogenous architectures. The diastereoselectivity and regioselectivity of pyridinium oxide cycloadditions was systematically investigated for the first time using complex substrates. Predictably high levels of diastereoselectivity and regioselectivity are observed, which can be attributed to minimization of steric (syn‐pentane) and torsional strain in the products. The reaction is reversible under the reaction conditions, and it is stereospecific with respect to the dipolarophile geometry.
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- Award ID(s):
- 1956401
- PAR ID:
- 10256763
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 27
- Issue:
- 12
- ISSN:
- 0947-6539
- Format(s):
- Medium: X Size: p. 4028-4032
- Size(s):
- p. 4028-4032
- Sponsoring Org:
- National Science Foundation
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