The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides

Emmanouil Broumidis; Christopher Thomson; Brendan Gallagher; Lia Sotorríos; Kenneth George McKendrick; Stuart Alan Macgregor; Martin J. Paterson; Janet Lovett; Gareth O. Lloyd; Georgina Margaret Rosair; Andreas Kalogirou; Panayiotis Koutentis; Filipe Vilela

doi:10.1021/acs.orglett.3c02673

The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides

Emmanouil Broumidis, Christopher Thomson, Brendan Gallagher, Lia Sotorríos, Kenneth George McKendrick, Stuart Alan Macgregor^*, Martin J. Paterson, Janet Lovett, Gareth O. Lloyd, Georgina Margaret Rosair, Andreas Kalogirou, Panayiotis Koutentis^*, Filipe Vilela^*

^*Corresponding author for this work

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Abstract

1,2,6-Thiadiazines treated with visible light and 3O2 under ambient conditions are converted into difficult-to-access 1,2,5-thiadiazole 1-oxides (35 examples, yields of 39–100%). Experimental and theoretical studies reveal that 1,2,6-thiadiazines act as triplet photosensitizers that produce ¹O₂ and then undergo a chemoselective [3 + 2] cycloaddition to give an endoperoxide that ring contracts with selective carbon atom excision and complete atom economy. The reaction was optimized under both batch and continuous-flow conditions and is also efficient in green solvents.

Original language	English
Pages (from-to)	6907-6912
Number of pages	6
Journal	Organic Letters
Volume	25
Issue number	37
Early online date	11 Sept 2023
DOIs	https://doi.org/10.1021/acs.orglett.3c02673
Publication status	Published - 22 Sept 2023

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Broumidis, E., Thomson, C., Gallagher, B., Sotorríos, L., McKendrick, K. G., Macgregor, S. A., Paterson, M. J., Lovett, J., Lloyd, G. O., Rosair, G. M., Kalogirou, A., Koutentis, P., & Vilela, F. (2023). The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides. Organic Letters, 25(37), 6907-6912. https://doi.org/10.1021/acs.orglett.3c02673

@article{2179a9722ece4a5f9a041d88fcac637b,

title = "The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides",

abstract = "1,2,6-Thiadiazines treated with visible light and 3O2 under ambient conditions are converted into difficult-to-access 1,2,5-thiadiazole 1-oxides (35 examples, yields of 39–100%). Experimental and theoretical studies reveal that 1,2,6-thiadiazines act as triplet photosensitizers that produce 1O2 and then undergo a chemoselective [3 + 2] cycloaddition to give an endoperoxide that ring contracts with selective carbon atom excision and complete atom economy. The reaction was optimized under both batch and continuous-flow conditions and is also efficient in green solvents.",

author = "Emmanouil Broumidis and Christopher Thomson and Brendan Gallagher and Lia Sotorr{\'i}os and McKendrick, {Kenneth George} and Macgregor, {Stuart Alan} and Paterson, {Martin J.} and Janet Lovett and Lloyd, {Gareth O.} and Rosair, {Georgina Margaret} and Andreas Kalogirou and Panayiotis Koutentis and Filipe Vilela",

note = "Funding Information: The authors thank Vapourtec for their excellent technical support. P.A.K. thanks Dr Nikos Chronakis (UCY) for mechanistic discussions related to the reactivity of singlet oxygen and superoxide. E.B. and C.G.T. are grateful to Heriot-Watt University and the EPSRC CRITICAT Centre for Doctoral Training (E.B. Ph.D. Studentship: EP/L016419/1, C.G.T Ph.D. Studentship: EP/LO14419/1) for funding and training. C.G.T. is grateful to the Heriot-Watt Annual Fund for financial support. P.A.K. and A.S.K. thank the University of Cyprus for the Internal Grant “Thiadiazine-Based Organic Photovoltaics”, and the Cyprus Research Promotion Foundation (Grant Nos. ΣΤΡΑΤΗΙΙ/0308/06, NEKYP/0308/02 ΥΓΕΙΑ/0506/19, and ΕΝΙΣΧ/0308/83). M.J.P. thanks the EPSRC for funding (Grant Nos. EP/T021675 and EP/V006746), and the Leverhulme Trust (Grant No. PG-2020-208). S.A.M. thanks the EPSRC for funding (Grant No. EP/T019867/1). Publisher Copyright: {\textcopyright} 2023 The Authors. Published by American Chemical Society",

year = "2023",

month = sep,

day = "22",

doi = "10.1021/acs.orglett.3c02673",

language = "English",

volume = "25",

pages = "6907--6912",

journal = "Organic Letters",

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publisher = "American Chemical Society",

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Broumidis, E, Thomson, C, Gallagher, B, Sotorríos, L, McKendrick, KG, Macgregor, SA, Paterson, MJ, Lovett, J, Lloyd, GO, Rosair, GM, Kalogirou, A, Koutentis, P & Vilela, F 2023, 'The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides', Organic Letters, vol. 25, no. 37, pp. 6907-6912. https://doi.org/10.1021/acs.orglett.3c02673

TY - JOUR

T1 - The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides

AU - Broumidis, Emmanouil

AU - Thomson, Christopher

AU - Gallagher, Brendan

AU - Sotorríos, Lia

AU - McKendrick, Kenneth George

AU - Macgregor, Stuart Alan

AU - Paterson, Martin J.

AU - Lovett, Janet

AU - Lloyd, Gareth O.

AU - Rosair, Georgina Margaret

AU - Kalogirou, Andreas

AU - Koutentis, Panayiotis

AU - Vilela, Filipe

N1 - Funding Information: The authors thank Vapourtec for their excellent technical support. P.A.K. thanks Dr Nikos Chronakis (UCY) for mechanistic discussions related to the reactivity of singlet oxygen and superoxide. E.B. and C.G.T. are grateful to Heriot-Watt University and the EPSRC CRITICAT Centre for Doctoral Training (E.B. Ph.D. Studentship: EP/L016419/1, C.G.T Ph.D. Studentship: EP/LO14419/1) for funding and training. C.G.T. is grateful to the Heriot-Watt Annual Fund for financial support. P.A.K. and A.S.K. thank the University of Cyprus for the Internal Grant “Thiadiazine-Based Organic Photovoltaics”, and the Cyprus Research Promotion Foundation (Grant Nos. ΣΤΡΑΤΗΙΙ/0308/06, NEKYP/0308/02 ΥΓΕΙΑ/0506/19, and ΕΝΙΣΧ/0308/83). M.J.P. thanks the EPSRC for funding (Grant Nos. EP/T021675 and EP/V006746), and the Leverhulme Trust (Grant No. PG-2020-208). S.A.M. thanks the EPSRC for funding (Grant No. EP/T019867/1). Publisher Copyright: © 2023 The Authors. Published by American Chemical Society

PY - 2023/9/22

Y1 - 2023/9/22

N2 - 1,2,6-Thiadiazines treated with visible light and 3O2 under ambient conditions are converted into difficult-to-access 1,2,5-thiadiazole 1-oxides (35 examples, yields of 39–100%). Experimental and theoretical studies reveal that 1,2,6-thiadiazines act as triplet photosensitizers that produce 1O2 and then undergo a chemoselective [3 + 2] cycloaddition to give an endoperoxide that ring contracts with selective carbon atom excision and complete atom economy. The reaction was optimized under both batch and continuous-flow conditions and is also efficient in green solvents.

AB - 1,2,6-Thiadiazines treated with visible light and 3O2 under ambient conditions are converted into difficult-to-access 1,2,5-thiadiazole 1-oxides (35 examples, yields of 39–100%). Experimental and theoretical studies reveal that 1,2,6-thiadiazines act as triplet photosensitizers that produce 1O2 and then undergo a chemoselective [3 + 2] cycloaddition to give an endoperoxide that ring contracts with selective carbon atom excision and complete atom economy. The reaction was optimized under both batch and continuous-flow conditions and is also efficient in green solvents.

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U2 - 10.1021/acs.orglett.3c02673

DO - 10.1021/acs.orglett.3c02673

M3 - Article

C2 - 37695021

SN - 1523-7060

VL - 25

SP - 6907

EP - 6912

JO - Organic Letters

JF - Organic Letters

IS - 37

ER -

The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides

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