5-iodo-l,2,3-triazoles

Most recently, Buckley et al. [35], have shown that the polymeric alkynylcopper(I) ladder complex [PhC=C-Cu] , can be used as heterogeneous precatalyst in the on water cliek reaction for the synthesis of 5-iodo-l,2,3-triazoles. However, important drawbacks were reported for this catalytic system when compared with complex 6 (i) high copper loadings were required (10 mol%), (ii) the cycloaddition reaction is restricted to iodophenylacetylene and benzylic azides, and (iii) significant level of protolysis was observed. 

A suggested catalytic cycle is shown in Scheme 24. A number of different ligands have also been used in copper(I)-catalysed reactitMis of terminal iodoalkynes that lead to the formation of 5-iodo-l, 2,3-triazoles the best ligand was found to be tris(l-t-butyltriazolylmethyl)amine, which was found to dramatically reduce the time taken for the reactions to proceed to completion [158]. 

Bogdan A.R., James K. Synthesis of 5-iodo-l,2,3-triazole-containing macrocycles using copper flow reactor technology. Org. Lett. 2011 13(15) 4060 063. 

The 4- and 5-amino-l,2,3-triazoles are diazotizable, e.g. the diazonium salt from 4-aminotriazole-5-carboxamide with potassium iodide gives the 4-iodo derivative, and that from 4-amino-l,5-diphenyltriazole gives 1,5-diphenyltriazole in ethanol (74AHC(16)33). 

In the series of 1,2,3-triazoles fast rearrangement of Af-bromo-4-methyl-1,2,3-triazole 33c to 4-methyl-5-bromo-l,2,3-triazole 57 is described [55LA(593)207], 1-Iodo-l, 2,3-triazole 34a yields 4,5-diiodo-l,2,3-triazole 58 on heating to 110°C in the presence of 3,5-dimethyl-l, 2,4-triazole as a halogen carrier (70ZC220) (Scheme 31). 

The iodo-promoted cyclization reaction of 4-allyl-5-phenyl-l,2,4-triazole-3(47/)-thione 344 gives a mixture of compounds 31 and 345 (Equation 66) <2004CHE1077>. 

The halogen metal exchange reaction between 7-bromo or 7-iodo-3-phenyltriazolopyrimidine 165 and butyllithium in iV,N,N, N -tetra-methylethylenediamine afforded the 7-lithio compound 166, whereas a similar reaction with the 7-chloro derivative 165 (R = H) gave the ring-fission product, 5-amino-l-phenyl-l//-l,2,3-triazole-4-carbonitrile 169 (91 CPB2793). Reaction of 166 with electrophiles such as benzaldehyde and ketones gave 170 and 167 respectively, together with 7,7 -bis[3-phenyl-3//-1,2,3-triazolo[4,5-d]pyrimidine] 168 (Scheme 34). 

TV-Iodo-1,2,4-triazole 49 in contrast to N-chloro and A -bromo derivatives does not react under these conditions (69KGS1114). Formation of 3-iodo-and 3,5-diiodo-l,2,4-triazole proceeds on heating to 150°C in the presence of 3,5-dimethyl-l,2,4-triazole as the halogen carrier (69ZC300 70ZC220). 

There were some literature reports on the reactions of T2,4-triazoles. 3-Bromo- and 3-iodo-N,S-dibenzyl-5-mercapto-l,2,4-triazoles 140 participated in Suzuki—Miyaura cross-coupling reactions with aryl, heteroaryl, and vinyl boronic acid derivatives to give 141, followed by deprotection with aluminum chloride to give 5-hetero(aryl)-3-mercapto-l,2,4-triazoles 142 (13TL4524). Multiple regioisomers of arylated 1,2,4-triazoles via C-H arylation could be obtained from judicious reactions of SEM- and THP-protected 1,2,4-triazoles (13JOC738). 

Two products were isolated 5-Iodo-l,3-diphenyl-l,2,4-triazole (47/39%) and 3-iodo-5-phenyl-1,2,4-triazole (10/37%). 

The reaction of 3-iodo-l-methyl-l,2,4-triazole with 2-methylbut-3-yn-2-ol (75IZV690) has been used to prepare 3-ethynyl-l-methyl-l,2,4-triazole (117 Scheme 38) and the isomeric 5-ethynyl-1-methyl isomer from the corresponding iodotriazole. 

An efficient method for the preparation of 5-iodo-l,4-disubstituted-1,2,3-triazole (23) with the dithiophosphate moiety has been realized by a multicomponent, one-pot reaction of azides with alkynes in the presence of the novel Cul/NBS catalytic system (Scheme 6) The high tolerance of various sensitive groups revealed potential applications of this method in organic synthesis and drug discovery. 

The fused oxazole derivative 100 was synthesized from 3-azido-3-deoxy-l,2 5,6-di-O-isopropylidene-a-D-allofuranose, the key final step being the reaction of methyl 3-amino-3-deoxy-5,6-0-isopropylidene-p-D-alloside with DMF dimethyl acetal. The annelated pyranoside 101 was obtained by cyclization of a branched chain hexosulose derivative, and the fused triazole-piperidinoses such as 102 were made by a radical cyclization of a 3-pyrazolo-6-iodo-sugar derivative. The spiro-isoxazohne 103 and related isomers have been synthesized by dipolar cycloadditions of mesitonitrile oxide to 2-deoxy-2-C-methyl-ene-pentonic acids, themselves available in five steps from D-mannitol. Intra-... 

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