Contrasting Responses of Pyrido[2,1-a]isoindol-6-ones and Their Sultam Counterparts to Photochemical Activation

• Published in: Journal of organic chemistry Vol. 74; no. 5; pp. 1982 - 1987
• Main Authors: Paquette, Leo A, Dura, Robert D, Modolo, Isabelle
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 06.03.2009; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Cyclization; Exact sciences and technology; General and physical chemistry; Heterocyclic compounds; Heterocyclic compounds with n hetero atom and also o and/or s, se, te hetero atoms; Heterocyclic compounds with only one n hetero atom and condensed derivatives; Isoindoles - chemical synthesis; Isoindoles - chemistry; Molecular Structure; Organic chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Physical Sciences; Preparations and properties; Pyridines - chemical synthesis; Pyridines - chemistry; Science & Technology; Stereoisomerism; Sulfanilamides - chemistry; SULFOXIDES; YNAMIDES; MIYAURA DOMINO REACTIONS; BICYCLIC SULTAM; THIENOPYRIDINES; TRICYCLIC SYSTEMS; CHEMISTRY; SULFONES; N-OXIDES; SELECTIVE FORMATION; Sulfur nitrogen heterocycle; Sigmatropic reaction; Regioselectivity; Nitrogen heterocycle; Lactam; Metathesis; Polymerization; Selectivity; Photochemical reaction; Allylic compound; Ring cleavage; Imide; Saccharin; Side chain; Sultam; Cyclization; Conjugated dienic compound; Irradiation; Dimer; Chemical synthesis; Dimerization; Sensitizer; Acetone; Excited state
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo802476c

A ring-closing metathesis-based strategy has allowed access to an unreported pair of pyridoisoindolones and their previously unknown sultam counterparts. The synthetic routing takes advantage of the ready availability of N-allylphthalimide and N-allylsaccharin and proceeds via the proper incorporation of small side chains into the heterocyclic ring. Positionally selective introduction of the conjugated diene functionality was realized efficiently. Detailed study of the excited-state chemistry of 7 and 8 showed both lactams to be subject to [4 + 2] dimerization under acetone-sensitized conditions. Different regioselectivities are involved, with the response of 8 being far more efficient than that exhibited by 7. No dimers could be isolated from the photolyzates of 9 and 10 under any conditions. While the latter sultam undergoes extensive polymerization, 9 is transformed via direct irradiation at 350 nm into 46 and 47 via [1,3]-sigmatropy involving the S−N bond and heterocyclic ring cleavage, respectively.