S3 1 H NMR and 13 C NMR spectra of S-alkylisothiourea 5a S4 1 H NMR and 13 C NMR spectra of S-alkylisothiourea 5b S5 1 H NMR and 13 C NMR spectra of S-alkylisothiourea 5c S6 1 H NMR and 13 C NMR spectra of S-alkylisothiourea 5d S7
The application of Cu (I)-catalyzed halogen atom transfer radical cyclization (ATRC) for the synthesis of two different series of chlorinated, heteroatom rich and differently fused tricyclic β-lactams has been demonstrated. N-substituted-3,4dihydropyrimidine-2(1H)-thiones synthesized by Biginelli reaction were used as starting materials for this synthetic pathway which upon S-allylation/alkylation furnished 2-allylthio/alkylthio-1,4-dihydropyrimidines (cyclic imines). Staudinger reaction of these cyclic imines with dichloroketene was employed to obtain the bicyclic dichloro-S-allyl/N-allyl-β-lactams, which upon subsequent Cu(I)-catalyzed ATRC produced two different series of tricyclic β-lactams. The difference in the relative behavior of N-allyl bicyclic dichloro-β-lactams and S-allyl bicyclic dichloro-β-lactams towards ATRC was also introspected in terms of their relative rates of cyclization, the amount of catalyst loading needed and the stabilities of tricyclic-β-lactams obtained after cyclization. To study the relative reactivity of Nallyl group and S-allyl group towards ATRC, the bicyclic dichloro-β-lactams having both S-allyl and N-allyl groups were synthesized. The intramolecular competitive experiments revealed the high reactivity of S-allyl group towards ATRC than the N-allyl group.[a] Dr. N. DawraMehr Chand Mahajan DAV College for Women Sector 36-A, Chandigarh,
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