ChemInform Abstract: Pseudohalogeno Metal Compounds. Part 65. Synthesis of Tetrazoles and Triazoles via 1,3‐Dipolar Cycloaddition to the Azido Ligands of Polymeric Cobalt(III) and Palladium(II) Complexes. Synthesis and Structure of 5‐Trichloromethyltetrazole.

Abstract

195 ChemInform Abstract The cycloaddition of nitriles (II) and (V) or the alkyne (VII) with the azide function of the polymeric Co complex (Ia) affords Co-heterocycle complexes of type (III), giving the free tetrazoles (IV), (VI) and triazole (VIII) on cleavage with HCl. Yields are generally low, however, if the product is neither sublimable nor soluble in ether. The above procedure gives access to the trichloromethyl derivative (IVa) (X-ray analysis: space group P21/c with Z=4; previous syntheses had failed because of the formation of explosive intermediates). Alternatively, the target heterocycles can be prepared by treatment of nitriles or (VII) with the complexes (Ib), (XI) (obtained from Merrifield's resin (IX)) or (XIII). The reaction of the latter with the isocyanide (XIV) gives the product (XV) containing a Co-C bond.

Compatibility of thioamides with reverse turn features: synthesis and conformational analysis of two model cyclic pseudopeptides containing thioamides as backbone modifications

“…The ether was decanted and the product dried in vacuo over KOH pellets for 24 h. The product was a thick, clear oil (1.71 g, 97.7% yield): Rf (A) 0.10, Rf(C) 0.18, Rf (E) 0.48. Boc-Pro*[CSNH]Gly-Pro-Gly-OEt (7). The thiodipeptide 5 (2.30 g, 7.98 mmol) was added to a flask containing 6 (2.70 g, 11.4 mmol) in DMF (20 mL).…”

“…HCI-ProMCSNH]Gly-Pro-Gly-OEt (8). Pseudotetrapeptide 7 (2.87 g, 6.10 mmol) was dissolved in 4 N HCl/dioxane (10 mL). The solution was stirred for 40 min.…”

“…For the synthesis of 2, Boc-Proi/-[CSNH]Gly-OEt (4) was deprotected with 4 N HCl/dioxane and coupled to Boc-Pro-Gly-OH (12) to afford Boc-Pro-Gly-Pro^[CSNH] in 84% yield. The pseudotetrapeptide was then elaborated in the same manner as Boc-Proi/*[CSNH ] G ly-Pro-Gly-OEt (7) to yield HCl-H-D-Phe-Pro-Gly-Proi/'[CSNH]Gly-OH (18). Cyclization of 18 was performed, and this reaction also represents a successful extension of an endothiopeptide from the C-terminus.…”

A Simple and Direct Method for the Palladium‐Catalyzed Oxidative Coupling of Unactivated Allylarenes with Classic Arenes

“…While this at least in principle proved to be true – 5‐trichloromethyl‐tetrazole has been synthesized in this way and found to be non‐explosive at ambient temperatures in contrast to literature reports [281, 315] – the yields are comparatively low as a rule. [35b, 280, 281, 308] (In our paper,35b we had already speculated that Cl/N 3 ‐exchange in Cl 3 CCN might have caused the serious explosion which occurred on attempting to prepare trichloromethyltetrazole from trichloroacetonitrile and sodium azide, a reaction which would not take place with an azidocobalt polymer. [281, 315] Actually, 20 years later, Banert and co‐workers reported the formation of the exciting high‐energy‐density molecule tetraazidomethane, CN 12 , from Cl 3 CCN and NaN 3 .…”

Platinum(iv) azido complexes undergo copper-free click reactions with alkynes

“… 4 – 6 A range of d-block azido complexes, including those of Mn( i ), 7 , 8 Fe( iii ), 9 Pd( ii ), 10 Pt( ii ), 10 – 15 Rh( iii ) 16 and Au( i ), 17 have been reported to undergo copper-free 1,3-dipolar cycloaddition or “click” reactions with carbon–carbon and carbon-heteroatom functional groups such as alkynes, isocyanides, isonitriles, nitriles, carbon disulphides and isothiocyanates. Electron-deficient alkynes such as dimethyl acetylenedicarboxylate (DMAD) and diethyl acetylenedicarboxylate (DEACD) are relatively reactive: Mo( ii ), 16 , 18 Co( iii ), 19 Fe( iii ) 19 , 20 Ru( ii ), 20 – 25 Pd( ii ) 26 – 28 and Ta 29 azido complexes all react with DMAD. Strain-promoted azide–alkyne cycloadditions (SPAAC) 30 , 31 are also an effective method for derivatising azido complexes.…”