Synthesis and stability of thermally labile 1,2-oxaphosphetane 2-oxides and 1,2-thiaphosphetane 2-sulfides (microreview)
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Synthesis and stability of thermally labile 1,2-oxaphosphetane 2-oxides and 1,2-thiaphosphetane 2-sulfides (microreview) Jiaxi Xu1* 1
State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, College of Chemistry, Beijing University of Chemical Technology, 15 Northern 3rd Ring Road East, Chaoyang District, Beijing 100029, People's Republic of China; е-mail: [email protected] Submitted May 8, 2020 Accepted July 4, 2020
Published in Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(8), 979–981
Synthesis and thermal stability of 1,2-oxaphosphetane 2-oxide and 1,2-thiaphosphetane 2-sulfide derivatives are discussed. This microreview covers the available synthetic methods of thermally labile 1,2-oxaphosphetane 2-oxides and 1,2-thiaphosphetane 2-sulfides and their fragmentation. The synthetic approaches may be classified in four distinct categories: cycloaddition, cyclization, fragmentation, and annulation. Introduction Phosphalactones are important biologically active compounds. Some phosphalactones have been discovered in natural products and have been demonstrated to act as enzyme inhibitors such as inhibitors of acetylcholinesterase, protein tyrosine phosphatases, and pancreatic cholesterol esterase.1 Recently, we developed an efficient method for the synthesis of δ-phosphalactones.2 1,2-Oxaphosphetane 2-oxides (β-phosphalactones) and 1,2-thiaphosphetane 2-sulfides (β-dithiophosphalactones) are important phosphoruscontaining analogs of oxetan-2-ones (β-lactones) and 1,2-oxathietane 2,2-dioxides (β-sultones). They are also valuable oxygen or sulfur surrogates of 1,2-azaphosphetidine 2-oxides and 2-sulfides, respectively.3 Although they can
be considered as a class of transition state analogs and inhibitors of β-lactamases, they are thermally labile.4 Recently, our research group has been focusing on the chemistry of four-membered heterocycles,5 and β-lactams6 as well as β-sultams7 have been widely investigated. Compared with the synthesis of β-phosphalactams and β-thiophosphalactams,3 β-phosphalactones and β-dithiophosphalactones have been paid less attention. Moreover, preparation of their analogs – 1,2-oxaphosphetane 2-sulfides and 1,2-thiaphosphetane 2-oxides have not been documented to date. This microreview introduces to the synthesis and stability of thermally labile derivatives of 1,2-oxaphosphetane 2-oxide and 1,2-thiaphosphetane 2-sulfide.
Cycloaddition The first documented synthesis of 1,2-oxaphosphetane 2-oxides 1 is the cycloaddition of aromatic aldehydes, cinnamaldehydes, and ketones to phosphenes, including diphenyl(phenyl)phosphene (diphenylmethylideneoxophenylphosphorane) and benzoyl(phenyl)(phenyl)phosphene (1-benzoylbenzylideneoxophenylphosphorane), generated in situ from (diphenylphosphoryl)diazophenylmethane and (diphenylphosphoryl)diazoacetophenone, respectively, via Wolff rearrangement under photoirradiation.8 The structures of 1,2-oxaphosphetane 2-oxides 1 were first assigned according to mass spectral analysis on the basis of the fragmentation products
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