942416-32-2Relevant articles and documents
Reactions of a cyclopentadienyl-amidinate titanium benzimidamido complex
Groom, Laura R.,Russell, Adam F.,Schwarz, Andrew D.,Mountford, Philip
supporting information, p. 1002 - 1019 (2014/03/21)
We report the first reactivity study of a transition-metal benzimidamido complex, namely Cp Ti{PhC(NiPr)2}{NC(ArF 5NOtBu} (5, ArF5= C6F5). Reaction with CO2 and tBuNCO gave the cycloaddition products CpTi{PhC(NiPr)2}{OC(O)N(C{ArF5}NO tBu)} and CpTi{PhC(NiPr)2}{OC(N tBu)N(C{ArF5}NOtBu)} (10), respectively, whereas with CS2 slow extrusion of ArF5CN from 5 occurred to ultimately form CpTi{PhC(NiPr)2}{SC(S)N(O tBu)}. Reaction of 5 with ArC(O)H (Ar = Ph, 4-C6H 4Me, 4-C6H4tBu, 4-C 6H4OMe, 4-C6H4NMe2, 4-C6H4CF3) also gave the isolable metallacyclic complexes CpTi{PhC(NiPr)2}{N(C{ArF5}NO tBu)C(Ar)(H)O} (13) via reversible [2 + 2] cycloaddition reactions. In contrast, reaction with HC(O)NMe2 formed Me 2N{NC(ArF5)NOtBu}H (16) within 1 h at room temperature. Upon heating, 10 and 13 also underwent retrocyclization, forming the organic products tBuNCNC(ArF5)NOtBu and ArC{NC(ArF5)NOtBu}H (14), respectively. Selected examples of 14 and 16 were studied by DFT and UV-visible spectroscopy. Addition of isonitriles tBuNC and XylNC (Xyl = 2,6-C6H 3Me2) to CpTi{PhC(NiPr)2}{NC(Ar) NOtBu} (Ar = ArF5 (5), 2,6-C6H 3F2 (ArF2)) afforded the σ adducts CpTi{PhC(NiPr)2}{NC(Ar)NOtBu}(CNR) (Ar = ArF5, R = tBu, Xyl (19); Ar = ArF2, R = Xyl). Subsequently, 19 formed CpTi{PhC(NiPr)2}{NC(NO tBu)C6F4N(Xyl)C}(F) (20) via C-F bond activation. Reaction of 5 with 2 equiv of B(ArF5)3 gave CpTi{PhC(NiPr)2}{ON(B{ArF5}3) C(ArF5)N(H)(B{ArF5}3)} with elimination of 2-methylpropene.
Highly efficient formation of nitriles and alkoxy radicals from N-alkoxybenziminoyl chlorides in solution
De Peter Lijser,Burke, Cassandra R.,Rosenberg, Jonathan,Hunter, Jordan
supporting information; experimental part, p. 1679 - 1684 (2009/10/01)
A series of N-alkoxybenziminoyl chlorides were synthesized and reacted with tributyltin hydride in the presence of AIBN to generate the corresponding N-alkoxybenziminoyl radicals. This methodology successfully generates the desired radicals, which undergo a rapid and highly efficient β-scission reaction, as shown by the formation of the corresponding nitriles and products derived from alkoxy radicals. The intermediate N -alkoxybenziminoyl radical could not be trapped by employing high concentrations of Bu3SnH or by using a hydrogen atom donating solvent such as toluene. The fast β-scission reaction was found to be independent of the structure of the iminoyl chloride. These results are different from studies on the similar N-alkyliminoyl radicals, which typically give products from both β-scission hydrogen atom transfer pathways. Using the data from this study as well as some reported rate constants for different hydrogen atom transfer (HAT) processes, we conclude that the lower limit for the rate constant for the β-scission process (kβ)in N-alkoxybenziminoyl radicals is 2.5 × 107 s-1.
Photolytic and radical induced decompositions of O-alkyl aldoxime ethers
McCarroll, Andrew J.,Walton, John C.
, p. 1868 - 1875 (2007/10/03)
Direct photolytic radical induced homolyses of O-alkyl arylaldoxime ethers (ArCH=NOR) were studied by EPR spectroscopy and by end product analyses. Initiating radicals (X·), including t-BuO·, t-BuS· , alkyl and Me3Sn·, added rapidly to the C=N double bond to give adduct oxyaminyl radicals (ArCHXN·OR) that could be observed and characterised by EPR spectroscopy. For O-alkyl arylaldoxime ethers containing H-atoms attached to the carbon adjacent to the ether oxygen (OR = OCHR12), t-BuO· radicals also abstracted this hydrogen to yield oxyalky radicals that underwent rapid β-scission to afford iminyl radicals (ArCHN·) and an aldehyde or ketone (R12CO). judged by the relative importance of ROH and ArCN amongst the products, abstraction of the iminyl hydrogen atom also took place to yield oximidoyl radicals (ArC·=NOR), although this could not be confirmed by EPR spectroscopic observation of these radicals. Thus, homolysis induced by t-BuO· radicals took place comparatively unselectively. Addition of the t-BuO· radical to the C=N double bond of oxime ethers was very fast, the rate constant being comparable to that for addition of the same radical to nitrones. Direct and photosensitised UV photolysis of O-alkyl arylaldoxime ethers gave alkoxyl and aryliminyl radicals in very low yields. Although traces of 2-methyl-tetrahydrofuran were detected from cyclisation of the pent-4-enyloxyl radical generated by direct photolysis of O-pent-4-enyl benzaldoxime, yields were too low for preparative purposes.
