Catalytic System‐Controlled Divergent Reaction Strategies for the Construction of Diversified Spiropyrazolone Skeletons from Pyrazolidinones and Diazopyrazolones

Abstract

A catalytic system‐controlled divergent reaction strategy was here reported to construct four types of intriguing spiroheterocyclic skeletons from simple and readily available starting materials via a precise chemical bond activation/[n+1] annulation cascade. The tetraazaspiroheterocyclic and trizazspiroheterocyclic scaffolds could be independently constructed by a selective N−N bond activation/[n+1] annulation cascade, a C(sp2)‐H activation/[4+1] annulation and a novel tandem C(sp2)‐H/C(sp3)−H bond activation/[4+1] annulation strategy, along with a broad scope of substrates, moderate to excellent yields and valuable transformations. More importantly, in these transformations, we are the first time to capture a N−N bond activation and a C(sp3)−H bond activation of pyrazolidinones under different catalytic system.

Catalytic System‐Controlled Divergent Reaction Strategies for the Construction of Diversified Spiropyrazolone Skeletons from Pyrazolidinones and Diazopyrazolones

“…Likewise,the optimal reaction conditions for 4aaand 5aa were also separately explored (see Support Information for details) and the results displayed that when using [Cp*RhCl 2 ] 2 (4.0 mol %), Na 2 CO 3 (1 equiv) in MeCN/H 2 O( 4/1) at 60 8 8C for 4hunder Air atmosphere (condition B) and [Cp*RhCl 2 ] 2 (4.0 mol %), AgOAc (2 equiv), citric acid (2 equiv), 4 MS (100 mg) in MeCN at 80 8 8Cf or 4h under Ar atmosphere (condition C) as their respective catalytic systems,t he products 4aa and 5aa could be effectively prepared with 79 %a nd 81 %, respectively.T heir structures were unambiguously confirmed by their 1 Ha nd 13 CNMR spectra, mass spectrometry,and X-ray crystallographic analyses. [16] With the optimized reaction conditions identified, we firstly investigated the scope of pyrazolidinones 1 and coupling partners 2 under the optimal reaction condition (condition A) to build these novel tetraazaspiro[4.5]dec-3-enes 3 via as elective N À Nb ond activation and [5+ +1] annulation route (Scheme 2). Generally,t his transformation was compatible with all referred substrates.B esides 3aa could be obtained with an excellent 90 %yield, whether we introduced halogen atoms (F,C la nd Br), electron-withdrawing groups (CF 3 ,CN) or electron-donating groups (CH 3 and OCH 3 )into 4-position of benzene ring of substrates 1,t he reaction efficiencies were still maintained at an excellent level (Scheme 2, 3ba-3ha).…”

“…Chemie Forschungsartikel 21500 www.angewandte.de mainly involved the production of 4aa,b ut had almost nothing to do with the production of 5aa.Additively,treating 1o and 2a under condition Co nly produced 6oa [16] in 53 % yield rather than the target spiro-heterocyclic product, which indicated the gem-dimethyl effect was critical to the formation of 5 (Scheme 6e). Tw ocontrol experiments showed that the pyrazolidinone 1a could be oxidized to iminium intermediate 1a' ',which was akey intermediate for the formation of product 5aa under the reaction condition C( Scheme 6j).…”

“…Fore xample,t reating 3aa with Lawessonsr eagent in toluene afforded spiropyrazole-5-thione 7 in 43 %yield. Theamide group of pyrazolone moiety in 3aa could be selectively reduced with DIBAL-H to provide spiropyrazoline derivatives 8 [16] and 9 in 66 %a nd 78 %y ields under different temperature.B esides,t he 6methyl and 6-allyl substituted subtetraazaspiro[4.5]dec-3enes (10 and 11)c ould be smoothly synthesized by using NaH to remove hydrogen from amino group followed by an ucleophilic attack on methyl iodide and allyl iodide. Moreover,t reating 3aa with NBS in CCl 4 could afford the selective brominated product 3dain 82 %yield, which offered an ew reaction site for further coupling reactions.T hen, the amide group with af ree NH moiety in 3aa could undergo as elective amide-imine interconversion, followed by ar eaction with dimethylcarbamoyl chloride to provide 12.U nexpectedly,c ompound 3aa could be further converted into amore intriguing fused heterocycle 13 [16] in 75 %yield under Zn(OTf) 2 at 120 8 8Co vernight.…”

“…By the way,t he structure of 6aa was confirmed by X-ray crystallographic analysis. [16] It seemed that the intermediate 6aa…”

Coupling partner-dependent unsymmetrical C–H functionalization of N-phenoxyacetamides leading to sophisticated spirocyclic scaffolds

“…Inspired by these elegant pioneering studies and continuing our interest on the functionalization of inert chemical bonds, 5,6 in this work we endeavored to design and explore the reactions of N -phenoxyacetamides with diazopyrazolones 7 and diazooxindoles 8 with the aim of obtaining new chemical entities that have potential pharmaceutical and material applications. Serendipitously, we found two unprecedented distinct reaction modes of N -phenoxyacetamides under the catalysis of Rh( iii ).…”