In this account we disclose a variety of simple strategies demonstrated in our laboratory in the last two decades for the assembly of diverse and intricate molecular frameworks containing spiro linkage(s) by using various metathesis protocols such as ring‐closing metathesis (RCM), ring‐opening cross‐metathesis (ROCM), ring‐closing enyne metathesis (RCEM) and ring‐rearrangement metathesis (RRM). Also, cycloaddition reactions ([2+2], [4+2] and [2+2+2]) and other key processes such as Claisen rearrangement (CR), Grignard addition, Fischer indolization (FI), Suzuki–Miyaura (SM) cross‐coupling and the retro‐Diels–Alder (rDA) reaction have been used as key steps to construct spirocycles.

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A protocol employing FeCl3 in the presence of glacial AcOH is described for the less nucleophilic aniline and its variants, bromoacetic acid and sterically hindered amino acids.

Herein, we summarize the synthetic approaches that have been developed for the synthesis of star‐shaped molecules. Typically, to design such highly functionalized molecules, simple building blocks are first assembled through trimerization reactions, starting from commercially available starting materials. Then, these building blocks are synthetically manipulated to generate extended star‐shaped molecules. We also discuss the syntheses of star‐shaped molecules that contain 2,4,6‐trisubstituted 1,3,5‐triazine or 1,3,5‐trisubstituted benzene rings as a central core and diverse substituted styrene, phenyl, and fluorene derivatives at their periphery, which endows these molecules with extended conjugation. A variety of metal‐catalyzed reactions, such as Suzuki, Buchwald–Hartwig, Sonogashira, Heck, and Negishi cross‐coupling reactions, as well as metathesis, have been employed to functionalize a range of star‐shaped molecules. The methods described herein will be helpful for designing a wide range of intricate compounds that are highly valuable in the fields of supramolecular chemistry and materials science. Owing to space limitations, we will not cover all of the publications on this topic. Instead, we will focus on examples that were reported by our research group and other relevant recent literature. Apart from the trimerization sequence, this Minireview has been structured based on the key reactions that were used to prepare the star‐shaped molecules and other higher analogues. Finally, some examples that do not fit into this classification are discussed.

Propanephosphonic acid anhydride (T3P ® ) is a prevailing coupling and dehydrating agent with many desirable properties which render it a reagent of choice for a plethora of reactions and, befittingly, its application in organic synthesis is rapidly increasing. Since its introduction as a peptide coupling agent in 1980, the realm of applications of T3P has expanded. Currently its use is found in a broad range of reactions, including condensation, functional group transformation, heterocycles preparation, rearrangements, and catalysis. It offers several advantages over traditional reagents, such as high yield, chemical and optical purity, broad functional group tolerance and easy work-up. The reagent is attractive for large-scale synthesis as well, and particularly so for multi-kilogram scale preparations of drug molecules. This article reviews the hitherto reported applications of T3P as a reagent in organic synthesis. Focus is also placed on the use of T3P for large-scale synthesis.

Here, we prepared several dipeptides containing 2aminoindane-2-carboxylic acid (Aic) and carried out further synthetic transformations. Synthesis and purification of modified peptides by using [2 + 2 + 2] cyclotrimerization is a challenging task. We are able to modify the unusual amino acids and peptide derivatives by late-stage incorporation of benzylhalo functionality. To incorporate benzylhalo moiety we used [2 + 2 + 2] cyclotrimerization in the presence of Mo(CO) 6 . These halo derivatives are potential substrates for further modification by Sonogashira reaction, Suzuki-Miyaura cross-coupling, sultine formation, and the Diels-Alder reaction sequence.

One-pot preparation of N a -protected amino/ peptide hydroxamic acids from corresponding carboxylic acids is described using uronium-type coupling reagent COMU. The present protocol is simple and mild conditions are used. Thus the resulting hydroxamic acids are obtained in good yields without racemization.

Rapid synthesis of acid azides via in situ generation of acid chlorides using CPICl as chlorinating agent from the corresponding N α -protected amino acids is described. Also the conversion of acid azides into ureidopeptides through the Curtius rearrangement under ultrasonication is delineated. The mildness of the protocol renders the acid-sensitive substrates to afford the corresponding amino acid azides and ureidopeptides in good yields. Diphenylcyclopropenone has also been recovered from the reaction mixture and reused.