Novel Strategies Towards Condenced Triazoles, Ferrocene Aminoacids, Conjugates And Selenosulfides

Abstract

Chapter 1: Facile entry into triazole fused tetrahydropyrazinones from amines and amino acids. In this chapter, A practical and high yielding regioselective synthesis of several new, enantiopure 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyrazin-6-ones is described starting from primary amines in a three step reaction sequence (alkylation, acylation, one-pot displacement with azide followed by cycloaddition) employing constrained intramolecular ‘click’ reaction as the key step. The method obviates chromatographic purification of products.

This methodology was also extended to the synthesis of diverse triazole fused tetrahydropyrazinones derived from amino acids. The scope of this methodology was extended by varying the alkyl as well as acyl components which furnished other triazole fused novel heterocycles.

Chapter 2: Facile entry into triazole fused heterocycles via sulfamidate derived azido-alkynes. Direct synthesis of condensed triazoles from diverse sulfamidates by ring opening of sulfamidates with sodium azide followed by one-pot propargylation and cycloaddtion furnished title compounds. The methodogy in general has been demonstrated on diverse sulfamidates derived from amino acids, amino acid derivatives to obtain a variety of triazole fused scaffolds.

In one example, a condensed triazole containing amino acid has been synthesized by ring opening of a sulfamidate derivative with propargyl amine. This methodology has also been extended to the synthesis of condensed triazoles derived from D-glucose.

Chapter 3: ‘Click Chemistry’ Inspired Synthesis of Novel Ferrocene-Amino acid, Peptide Conjugates. In this chapter synthesis of a wide range of ferrocene-amino acid and peptide conjugates in excellent yield is presented. Conjugation is established via copper catalyzed Huisgen 1,3-dipolar cycloaddition. Two complementary strategies were employed for conjugation, one involving cycloaddition of amino acid derived azides with ethynyl ferrocene and the other involving cycloaddition between amino acid derived alkynes with ferrocene derived azides.

Labeling of amino acids at multiple sites with ferrocene is discussed. A new route to 1, 1’ unsymmetrically substituted ferrocene conjugates is reported. A novel ferrocenophane is accessed via bimolecular condensation of amino acid derived bis alkyne with azide.

The electrochemical behavior of a few selected ferrocene conjugates has been studied by cyclic voltammetry. Chapter 4: Click Chemistry inspired Synthesis of Ferrocene Amino acids and other derivatives. This work reports the synthesis of a wide range of ferrocenyl-amino acids and other derivatives in excellent yield.

Diverse amino acid containing azides were synthesized and ligated to ferrocene employing click reaction to access ferrocenyl amino acids. Chiral alcohols, esters, diols

amines containing azido group were tagged to ferrocene via click reaction to generateferrocene derived chiral derivatives. A novel strategy for direct incorporation of ferrocene into a peptide and a new route to 1, 1’ disubstituted ferrocene amino acid derivative are reported. Synthesis of mono and disubstituted ferrocene derivatives employing ferrocene derived azides is also described. Chapter 5: Convenient synthesis of Ferrocene Conjugates mediated by Benzyltriethylammonium Tetrathiomolybdate in a multi-step tandem process. The synthesis of a wide range of ferrocene derived sulfur linked mono and disubstituted Michael adducts and conjugates mediated by benzyltriethylammonium tetrathiomolybdate in a tandem process is reported. New route to access acryloyl ferrocene and 1,1’-bis acryloyl ferrocene is discussed.

Conjugation of amino acids to ferrocene is established via their Nand Ctermini and also via side chain employing conjugate addition as key step to furnish monovalent and divalent conjugates. This methodology has also been extended to access several ferrocene carbohydrate conjugates.

The electrochemical behavior of a few selected ferrocene conjugates has been studied by cyclic voltammetry. Finally, 1,1’-bis acryloyl ruthenocene was synthesized and it was utilized for the preparation of ruthenocene-carbohydrate conjugate in good yield. Chapter 6: Formation of Intramolecular S-Se bond mediated by tetrathiomolybdate. In this chapter, we have disclosed our preliminary results on reactivity of tetrathiomolybdate towards compounds containing both thiocyanate and selenocyanate functionalities. Several such compounds have been synthesized from the corresponding dibromides in two steps.

We have observed selective reductive dimerization of selenocyanate over thiocyanate. In all the cases we also obtained seleno-sulfides via disulfide diselenide exchange reaction upon addition of excess tetrathiomolybdate.

In the case of substrates on benzene scaffold, disulfide and diselenide bridged macrocycles were obtained apart from seleno sulfides whereas in the case of ferrocene derived substrates, formation of macrocycles was not observed. A tentative mechanism for the formation of these novel seleno sulfides is also discussed.(For structural formula pl see the pdf file)