Construction of NH-Unprotected Spiropyrrolidines and Spiroisoindolines by [4+1] Cyclizations of γ-Azidoboronic Acids with Cyclic N-Sulfonylhydrazones

Syntheses and medicinal chemistry of spiro heterocyclic steroids

There is compelling evidence that incorporating a heterocyclic moiety into a steroid can alter its pharmacological and pharmacokinetic properties, driving intense interest in the synthesis of such hybrids among research groups. In this review, we present an overview of recent synthetic methodologies, spanning the period from 2000 to 2023, for the preparation of spiro heterocyclic steroids. The compounds surveyed encompass four-, five-, six-, and seven-membered heterocycles appended to various positions of steroidal backbones, with spirocycles containing oxygen, nitrogen, and sulfur atoms being predominant. The outlined synthetic procedures emphasize the pivotal steps for constructing the heterocycles, often accompanied by a detailed account of the overall synthesis pathway. The review encompasses innovative compounds, including bis-steroids linked by a spiro heterocycle and steroids conjugated to heterocyclic moieties containing three or more (hetero)cycles. Moreover, many compounds are accompanied by data on their biological activities, such as antiproliferative, antimalarial, antimicrobial, antifungal, steroid antagonist, and enzyme inhibition, among others, aimed at furnishing pertinent insights for the future design of more potent and selective drugs.

Lead-oriented synthesis of epigenetic relevant scaffolds

A simple and rational method to rank lead-likeness of molecules using continuous evaluation functions was hereby developed. This strategy proved to be competitive against known methods and finally helped in driving synthetic efforts towards candidates of interest for epigenetic applications against HDAC6, BRD4 and EZH2.

Synthesis of substituted benzylboronates by light promoted homologation of boronic acids with N-sulfonylhydrazones

The synthesis of benzylboronates by photochemical homologation of boronic acids with N-tosylhydrazones under basic conditions is described. The reaction involves the photolysis of the N-tosylhydrazone salt to give a diazoalkane followed by the geminal carboborylation of the diazoalkane. Under the mild reaction conditions, the protodeboronation of the unstable benzylboronic acid is circumvented and the pinacolboronates can be isolated after reaction of the benzylboronic acid with pinacol. The metholodogy has been applied to the reactions of alkylboronic acids with N-tosylhydrazones of aromatic aldehydes and ketones, and to the reactions of arylboronic acids with N-tosylhydrazones of aliphatic ketones. Moreover, the employment of the DBU/DIPEA bases combination allows for homogeneous reactions which have been adapted to photochemical continuous flow conditions. Additionally, the synthetic versatility of boronates enables their further transformation via Csp3-C or Csp3-X bond forming reactions converting this methodology into a novel method for the geminal difunctionalization of carbonyls via N-tosylhydrazones.

DBU-Catalyzed Ring Expansion or Ene-amine Formation Involving δ-Acetoxy Allenoates and N-Sulfonyl Hydrazides

DBU-catalyzed spiro-annulation and concomitant ring expansion/domino reaction of δ-acetoxy allenoates with cycl-2-ene-N-sulfonyl hydrazides afford ring-expanded (5 → 6, 6 → 7, and 7 → 8) products. By contrast, cycl-3-ene/ane-N-sulfonyl hydrazones under similar conditions deliver pyrazole cores with the same allenoate that involves allylic elimination in which δ-acetoxy allenoate serves as 3C-synthon. The key spirocyclic intermediates, as well as dienyl-amine intermediates, are isolated and characterized. An extension to (R)-(-)-carvone-derived sulfonyl hydrazide also led to ring expansion and gave pyrazoloazepine.

Synthesis of Isoindole N-Oxides by Palladium-Catalyzed C-H Functionalization of Aldonitrones

A palladium-catalyzed strategy for isoindole N-oxide ring construction by C-H functionalization of aldonitrones is described. Our protocol is of general character, providing isoindole N-oxides with a variety of functional groups, including very sterically congested products. Further transformations into spirocyclic isoindolines, isoindoles, or a polycyclic isoquinolinium salt have been demonstrated as well. A mechanistic study suggests that the catalytic process proceeds via a Heck-type addition to the double C═N bond.