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Volumn 71, Issue 8, 2006, Pages 3192-3197

Generation and cyclization of unsaturated carbamoyl radicals derived from S-4-pentynyl carbamothioates under tin-free conditions

Author keywords

[No Author keywords available]

Indexed keywords

BENZENE; MOLECULAR ORIENTATION; SUBSTITUTION REACTIONS; SULFUR; SYNTHESIS (CHEMICAL);

EID: 33645797303     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo0602064     Document Type: Article
Times cited : (43)

References (47)
  • 1
    • 0004269715 scopus 로고    scopus 로고
    • Renaud, P., Sibi, M. P., Eds.; Wiley-VCH: Weinheim
    • For a comprehensive review on synthetic radical chemistry, see: Radicals in Organic Synthesis; Renaud, P., Sibi, M. P., Eds.; Wiley-VCH: Weinheim, 2001; Vols. 1 and 2.
    • (2001) Radicals in Organic Synthesis , vol.1-2
  • 20
    • 0001362069 scopus 로고
    • N-Substituted carbamoyl radicals are known to exist as mixtures of the respective E- and Z-conformers; see: Sutcliffe, R.; Ingold, K. U. J. Am. Chem. Soc. 1981, 103, 7686. The predominance of rotamers unfavorable to ring formation in secondary carbamoyl radicals is a possible reason for the known reluctance of these radicals to undergo cyclization onto alkenes; see refs 8 and 9a.
    • (1981) J. Am. Chem. Soc. , vol.103 , pp. 7686
    • Sutcliffe, R.1    Ingold, K.U.2
  • 34
    • 0346208460 scopus 로고    scopus 로고
    • and ref 9a
    • In principle, a formally 6-endo-cyclized benzylic radical might result from ring expansion of the initial 5-exo ring-closed β-oxoindolinylmethyl radical via 3-exo cyclization onto the adjacent carbonyl group and subsequent β-scission of the ensuing alkoxyl radical; see: Chatgilialoglu, C.; Crich, D.; Komatsu, M.; Ryu, J. Chem. Rev. 1999, 99, 1991 and ref 9a.
    • (1999) Chem. Rev. , vol.99 , pp. 1991
    • Chatgilialoglu, C.1    Crich, D.2    Komatsu, M.3    Ryu, J.4
  • 35
    • 33645793184 scopus 로고    scopus 로고
    • note
    • No evidence for any β-elimination of tosyl radical was gained in previous cyclization reactions of N-tosylcarbamoyl radicals derived from corresponding selenocarbamates, see ref 8.
  • 36
    • 33645768012 scopus 로고    scopus 로고
    • note
    • Similar to the analogue 3 (ref 2h), the tosylated tetrahydrothiophene 8 occurred as a mixture of (E)- and (Z)-isomer in unestablished ratio.
  • 38
    • 33645788209 scopus 로고    scopus 로고
    • note
    • A control experiment established that tetrahydrothiophene 3 can be converted to the tosylated analogue 8 upon radical reaction with TsSPh/AIBN in refluxing benzene.
  • 39
    • 33645792242 scopus 로고    scopus 로고
    • note
    • A control experiment interestingly showed that the radical chain reaction of S-4-pentynyl benzenecarbothioate with TsSPh/AIBN in refluxing benzene cleanly afforded compound 8 as well as S-phenyl benzenecarbothioate.
  • 40
    • 33645767310 scopus 로고    scopus 로고
    • note
    • For unclear reasons, the carbamoyl radical 2g could also undergo significant decarbonylation leading to reduced N-(2-isopropenylphenyl)-4- methylbenzenesulfonamide (25%).
  • 42
    • 33645772559 scopus 로고    scopus 로고
    • note
    • Comparable yields of pyrrolydinones and indolinones have been reported in previous cyclizations of N-benzylcarbamoyl radicals derived from 1-benzylcarbamoyl-1-methylcyclohexa-2,5-dienes; see ref 9a,b. However, a better yield of pyrrolidinone 4a was achieved when the carbamoyl radical 2a was generated by UV photolysis of the corresponding oxime oxalate amide; see ref 10a.
  • 44
    • 33645783591 scopus 로고    scopus 로고
    • note
    • In principle, pyrrolidinone 4h might also arise from ring enlargement of the initial 4-exo ring-closed β-oxoazetidinylmethyl radical, see ref 12.
  • 45
    • 33645795347 scopus 로고    scopus 로고
    • note
    • Only minor amounts of a mixture of unidentified products were obtained.
  • 46
    • 33645797246 scopus 로고    scopus 로고
    • note
    • 13C NMR spectra.
  • 47
    • 33645780070 scopus 로고    scopus 로고
    • note
    • 4J of the vinylic proton with the allylic-like ring protons should be larger for the (E)- than for the (Z)-isomer; see ref 2h.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.