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Diazo-transfer reaction with diphenyl phosphorazidate


Villalgordo, Jose M; Enderli, Adelheid; Linden, Anthony; Heimgartner, Heinz (1995). Diazo-transfer reaction with diphenyl phosphorazidate. Helvetica Chimica Acta, 78:1983-1998.

Abstract

Diphenyl phosphorazidate (DPPA) was used as the azide source in a one-pot synthesis of 2,2-disubstituted 3-amino-2H-azirines 1 (Scheme 1). The reaction with lithium enolates of amides of type 2, bearing two substituents at C(2), proceeded smoothly in THF at 0°; keteniminium azides C and azidoenamines D are likely intermediates. Under analogous reaction conditions, DPPA and amides of type 3 with only one substituent at C(2) gave 2-diazoamides 5 in fair-to-good yield (Scheme 2). The corresponding 2-diazo derivatives 6-8 were formed in low yield by treatment of the lithium enolates of N,N-dimethyl-2-phenylacetamide, methyl 2-phenylacetate, and benzyl phenyl ketone, respectively, with DPPA. Thermolysis of 2-diazo-N-methyl-N-phenylcarboxamides 5a and 5b yielded 3-substituted 1,3-dihydro-N-methyl-2H-indol-2-ones 9a and 9b, respectively (Scheme 3). The diazo compounds 5 - 8 reacted with 1,3-thiazole-5(4H)-thiones 10 and thiobenzophenone (13) to give 6-oxa-1,9-dithia-3-azaspiro[4.4]nona-2,7-dienes 11 (Scheme 4) and thiirane-2-carboxylic acid derivatives 14 (Scheme 5), respectively. In analogy to previously described reactions, a mechanism via 1,3-dipolar cycloaddition, leading to 2,5-dihydro-1,3,4-thiadiazoles, and elimination of N2 to give the ‘thiocarbonyl ylides’ of type H or K is proposed. These dipolar intermediates with a conjugated C=O group then undergo either a 1,5-dipolar electrocyclization to give spiroheterocycles 11 or a 1,3-dipolar electrocyclization to thiiranes 14.

Abstract

Diphenyl phosphorazidate (DPPA) was used as the azide source in a one-pot synthesis of 2,2-disubstituted 3-amino-2H-azirines 1 (Scheme 1). The reaction with lithium enolates of amides of type 2, bearing two substituents at C(2), proceeded smoothly in THF at 0°; keteniminium azides C and azidoenamines D are likely intermediates. Under analogous reaction conditions, DPPA and amides of type 3 with only one substituent at C(2) gave 2-diazoamides 5 in fair-to-good yield (Scheme 2). The corresponding 2-diazo derivatives 6-8 were formed in low yield by treatment of the lithium enolates of N,N-dimethyl-2-phenylacetamide, methyl 2-phenylacetate, and benzyl phenyl ketone, respectively, with DPPA. Thermolysis of 2-diazo-N-methyl-N-phenylcarboxamides 5a and 5b yielded 3-substituted 1,3-dihydro-N-methyl-2H-indol-2-ones 9a and 9b, respectively (Scheme 3). The diazo compounds 5 - 8 reacted with 1,3-thiazole-5(4H)-thiones 10 and thiobenzophenone (13) to give 6-oxa-1,9-dithia-3-azaspiro[4.4]nona-2,7-dienes 11 (Scheme 4) and thiirane-2-carboxylic acid derivatives 14 (Scheme 5), respectively. In analogy to previously described reactions, a mechanism via 1,3-dipolar cycloaddition, leading to 2,5-dihydro-1,3,4-thiadiazoles, and elimination of N2 to give the ‘thiocarbonyl ylides’ of type H or K is proposed. These dipolar intermediates with a conjugated C=O group then undergo either a 1,5-dipolar electrocyclization to give spiroheterocycles 11 or a 1,3-dipolar electrocyclization to thiiranes 14.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Uncontrolled Keywords:Physical and Theoretical Chemistry, Inorganic Chemistry, Organic Chemistry, Biochemistry, Drug Discovery, Catalysis
Language:English
Date:1995
Deposited On:04 Dec 2013 14:02
Last Modified:18 Aug 2018 12:27
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Swiss National Science Foundation, F. Hoffmann-La Roche AG, Basel, Prof. Hans E. Schmid-Stiftung
OA Status:Closed
Publisher DOI:https://doi.org/10.1002/hlca.19950780807
Project Information:
  • : FunderSNSF
  • : Grant ID
  • : Project TitleSwiss National Science Foundation
  • : Funder
  • : Grant ID
  • : Project TitleF. Hoffmann-La Roche AG, Basel
  • : Funder
  • : Grant ID
  • : Project TitleProf. Hans E. Schmid-Stiftung

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