Tetrazoles 5-amino- from

The short Sanofi route to irbesartan (3) is outlined in Scheme 9.6. Dihydroimidazolone 27, which is prepared from the reaction of 1-amino-cyclopentanecarboxylic acid ester (25) with ethyl pentanimidate (26) in the presence of acetic acid in refluxing xylene, is alkylated with biphenylbenzyl bromide 18 in the presence of sodium hydride in DMF to give 28. Finally, the synthesis of irbesartan (3) is completed by the tetrazole formation from reaction of the nitrile group of 28 with tributyltin azide in refluxing xylene. [See Bernhart et al. (1993a, b).]... 

In oligonucleotide chemistry, alcoholysis of phosphoramidites is widely used for the construction of the polymers from monomeric sugars (Scheme 2.136) [46]. The reaction is usually catalyzed by Lff-tetrazol (TetH), which in the first step protonates the amino group. Subsequently, the tetrazole anion replaces the amine. The dinucleoside phosphite is formed by the final reaction with the alcoholic group of a second nucleoside. Since the formation of the tetrazole phosphoramidite from the intermediate salt is rate-determining, the catalyst... 

The 1 1 complexes arising from interaction of the hydride (as a complex with ether or trimethylamine) and various tetrazole derivatives are explosive. Tetrazoles mentioned are 2-methyl-, 2-ethyl-, 5-ethyl-, 2-methyl-5-vinyl-, 5-amino-2-ethyl-, l-alkyl-5-amino-, and 5-cyano-2-methyl-tetrazole. 

Two variations of the transformation of 3-acyltetrazoles into oxadiazoles are useful from a synthetic point of view. The first transformation involves the reaction of tetrazole with diketene. In the second, the sodium salt of the tetrazole is treated with oxalyl chloride. UV irradiation of some 3-amino-l,2,4-oxadiazoles leads to the formation of the corresponding 2-amino-l,3,4-oxadiazoles <1996CHEC-II(4)268>. 

The synthetic pathway to tetrazolo[l,5-tf]pyrimidines starting from 5-amino-tetrazoles has already been discussed in CHEC-II(1996) <1996CHEC-II(8)465>. During the recent period of time, several modifications of this approach have been described. The obtained products - among them some partly saturated derivatives - and the applied reagents as well as yields and references are summarized in Table 9. 

Agrawal and co-workers reported the synthesis of two tetrazole-based explosives, namely, 5-picrylamino-l,2,3,4-tetrazole " (PAT) (149) and 5,5 -styphnylamino-l,2,3,4-tetrazole (SAT) (150) from the reaction of 5-amino-1,2,3,4-tetrazole (148) with picryl chloride and styphnyl chloride respectively. These explosives have been studied for their thermal and explosive properties. The thermal stability of SAT (exotherm peak at 123 °C) is lower than PAT (exotherm peak at 185 °C), which is possibly attributed to the decreased electron-withdrawing power of the picryl group by being attached to two tetrazole units. PAT and SAT have calculated VODs of 8126 m/s and 8602 m/s respectively. ... 

Cefoperazone Cefoperazone, (6/ ,7/ )-7-[(/ )-2-(4-ethyl-2,3-dioxo-l-piperazincarboxam-ido)-2-(p-hydroxyphenyl)acetamido]-3-[[(l-methyl-l//-tetrazol-5-yl)thio]methyl]-8-oxo-5-thia-l-azabicyclo[4.2.0]oct-2-en-2-carboxylic acid (32.1.2.84), is synthesized by acylating 7-amino-3-(l-methyl-l,2,3,4-tetrazol-5-yl)-thiomethyl-3-cefem-4-carboxylic acid (32.1.2.24) with a mixed anhydride synthesized from ethyl chloroformate and a-(4-ethylpiperazin-2,... 

Azetidin-2-ones with general strueture (299) have been synthesized from the reaetion of 5-aminotetrazole with amino aeid esters <84TL91l) and from addition of glyeine enolates to N-(tetrazol-5-yl)imines <84TL3849>. A number of these eompounds displayed moderate to potent... 

Bamberger, Padova, and Ormerod reported in 1926 an interesting but incomplete study of several unusual products obtained from 5-amino-2,3-diaryl-l,2,3,4-tetrazolium salts (400). Recently this topic has been the subject of a detailed study by I. S. Smith, and the existence of several derivatives of meso-ionic l,2,3,4-tetrazol-5-imines (399) has now been firmly established. Comparison of Smith s recent results with the earlier results of Bamberger et alP is instructive. 

The seemingly complex imidazolone (78-3) is in fact obtained in a single step by reaction of the amino-ester (78-1) with the iminoether (78-2) derived from capro-nitrile. The relatively acidic proton on the heterocyclic ring is next removed by reaction with sodium hydride. This anion is then alkylated with the same biphenyl-methyl bromide (77-2) that was used to prepare losartan to afford (78-4). The nitrile group is in this case converted to the tetrazole by means of tributyltin azide, a reagent that involves milder conditions than the traditional acidic medium used to generate hydrazoic acid. Thus, treatment of (78-4) with the tin reagent affords irbesartan (75-5) [82]. 

---