2305-79-5Relevant articles and documents
Diazophosphonates: Effective Surrogates for Diazoalkanes in Pyrazole Synthesis
Green, Michael T.,Hayes, Christopher J.,Inman, Martyn,Lewis, William,Moody, Christopher J.,Nicolle, Simon M.,Ruffell, Katie,Smith, Frances R.
, p. 13703 - 13708 (2021/09/09)
Diazophosphonates, readily prepared from α-ketophosphonates by oxidation of the corresponding hydrazones in batch or in flow, are useful partners in 1,3-dipolar cycloaddition reactions to alkynes to give N-H pyrazoles, including the first intramolecular examples of such a process. The phosphoryl group imbues a number of desirable properties into the diazo 1,3-dipole. The electron-withdrawing nature of the phosphoryl stabilizes the diazo compound making it easier to handle, whilst the ability of the phosphoryl group to migrate readily in a [1,5]-sigmatropic rearrangement enables its transfer from C to N to aromatize the initial cycloadduct, and hence its facile removal from the final pyrazole product. Overall, the diazophosphonate acts as a surrogate for the much less stable diazoalkane in cycloadditions, with the phosphoryl group playing a vital, but traceless, role. The cycloaddition proceeds more readily with alkynes bearing electron-withdrawing groups, and is regiospecific with asymmetrical alkynes. The potential of diazophosphonates for use in bioorthogonal cycloadditions is demonstrated by their facile addition to strained alkynes.
Thermal rearrangements of 3,3-spiroalkylated pyrazoles: Ring expansion and novel cases of sequential 1,5-shifts
Yen, Yao-Pin,Chen, Shih-Feng,Heng, Zan-Cheng,Huang, Jen-Chieh,Kao, Li-Chun,Lai, Ching-Cheng,Liu
, p. 1859 - 1871 (2007/10/03)
A 3,3-spiro-(cyclopentyl)pyrazole containing electron withdrawing ester groups undergoes readily ring expansion in the form of the van Alphen-Huettel rearrangement. Subsequent post van Alphen-Huettel rearrangement involved a sequence of 1,5-shifts different from that suggested earlier. Reactive intermediates have been isolated and identified. The corresponding phenyl analog does not exhibit post van Alphen-Huettel rearrangement. A rationale for the different behavior is offered. X-Ray crystallography has been applied to differentiate between structurally similar product.
Intermediates for making N-aryl and N-heteroarylamide and urea derivatives as inhibitors of acyl coenzyme A: cholesterol acyl transferase (ACAT)
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, (2008/06/13)
Compounds of the formula STR1 wherein R21 and R22 are as defined in the specification which are intermediates useful in the preparation of compounds of the formula STR2 and the pharmaceutically acceptable salts thereof, wherein Q and R1 are as defined in the specification. The compounds of formula I are inhibitors of acyl coenzyme A: cholesterol acyltransferase (ACAT) and are useful as hypolipidemic and antiatherosclerosis agents.