C.—The constitution of the diazo-compounds

Abstract

By JOHN CANNELL GAIN.ALTHOUGH the long controversy between Hantzsch and Bamberger on this subject apparently came to a n end some few years ago, and many chemists have accepted the views of the former, yet it would appear that there is still some uncertainty of opinion with regard to the constitution of these substances.The stereochemical hypothesis of the constitution of the metallic diazo-derivatives (also cyanides, stc.), so stoutly advocated by Hantzsch, has been sharply criticised by Bamberger, von Pechmann, Blomstrand, and Armstrong, but t'he re-introduction of Blomstrand's formula for the diazo-salts by Bamberger in 1895 has met with hardly any opposition.Although this formula, for example, C,H5*NCliN, advocated, as i t has been, by no less tban three chemists independently (Blomstrand, 1869, Strecker, 1871, and Erlenmeyer, 1874, was rejected on the ground that it did not explain the formation of phenylhydrazine from diazobenzene chloride by reduction as did Kekulk's formula, C,H, *N :NCl, i t must be admitted t h a t the reasons given by Bamberger for discarding the latter were slight. This chemist indeed only advanced the old criticism of Blomstrand that Kekuld's formula was t h a t of a chloride of nitrogen and as such was improbable. Apparently Bamberger was not quite sure as to which of the two formulae, C,H,*NCliN and C,H,*NiNCl, was the more preferable, but finally chose the former. Hantzsch did not at first agree with this view ; he regarded diazobenzene chloride as a syn-diazo-compound, but soon rejected this and agreed with Bamberger in adopting the Blomstrand formula.It is necessary to point out here that Blomstrand's formula was

Phosphine-Free and Reusable Palladium Nanoparticles-Catalyzed Domino Strategy: Synthesis of Indanone Derivatives

“…Transition-metal-catalyzed C–C bond formation reactions are well-accepted synthetic strategies for the synthesis of rich biologically active pharmaceuticals and natural products. , Recently, the use of metal-carbenoid involving domino reactions holds tremendous promise to construct cyclic architectures via multiple C–C bond formation in a single step. − While diazo compounds have been primarily used as carbene precursors, they lessen synthetic strategies due to instability and explosive nature in the absence of electron withdrawing groups. , In this regard, stable and safe N -tosylhydrazones have been introduced as alternative carbene precursors. − Utilizing N -tosylhydrazones, a few Pd-catalytic cycles have been reported that converge carbene migratory insertion with other transformations for the synthesis of cyclic skeletons (Scheme a). − …”

Johann Peter Griess FRS (1829–88): Victorian brewer and synthetic dye chemist

“…The structure that acknowledged the salt nature of the diazonium group was proposed by C. W. Blomstrand in 1869 and was generally accepted by 1895, although debate persisted for some years. 67 Interest in using Griess's method was considerable, and his former mentor, Hofmann, and colleague, Caro, were notable in continuing to produce new dyes, leading to arguments of priority, which also highlighted the contrasting needs of an open patent system and secrecy mentioned above. Later, soluble sulphonic acid derivatives of azo dyes were produced by F. Z. Roussin (1876), especially orange dyes, but they were not patented, seemingly under the mistaken belief that rivals would find it difficult to replicate the synthesis, an error that was soon exposed.…”

Palladium-Catalyzed Intermolecular Carbene Insertion Prior to Intramolecular Heck Cyclization: Synthesis of 2-Arylidene-3-aryl-1-indanones

“…In the current scenario, cross-coupling reactions that involve metal carbene species have emerged as a powerful strategy for the formation of C–C bonds. , Diazo compounds are widely utilized as a precursor for the generation of metal carbene species . However, the uncertain explosive nature and instability of diazo compounds without electron-withdrawing groups has forced the search for alternative precursors . In recent years, N -tosylhydrazones have emerged as convenient precursors for the in situ generation of unstable diazo compounds. , Palladium has been exploited as a potent catalyst in this field, where the reaction is considered to proceed via migratory insertion of a palladium carbene intermediate. , In particular, domino C–C bond formations triggered by Pd-catalyzed migratory insertion are very attractive and productive, as structural complexity can be achieved in a single operation …”