Divergent Construction of Pyrazoles via Michael Addition of N‑Arylhydrazones to 1,2-Diaza-1,3-dienes

partially_open4noThe base (NaH)-promoted Michael addition of N-arylhydrazones (AHs) with 1,2-diaza-1,3-dienes (DDs) produces unprecedented β-azohydrazone adducts. Strategically, the use of AHs as acyl anion equivalents (d1 synthon) and DDs as α-electrophiles (a2 synthon) of carbonyl compounds open the way to two important classes of pyrazole compounds.embargoed_20160409Serena mantenuto; Fabio Mantellini; Orazio Attanasi; Gianfranco FaviMantenuto, Serena; Mantellini, Fabio; Attanasi, ORAZIO ANTONIO; Favi, Gianfranc

Divergent Construction of Pyrazoles via Michael Addition of <i>N</i>‑Arylhydrazones to 1,2-Diaza-1,3-dienes

The base (NaH)-promoted Michael addition of <i>N</i>-arylhydrazones (AHs) with 1,2-diaza-1,3-dienes (DDs) produces unprecedented β-azohydrazone adducts. Strategically, the use of AHs as acyl anion equivalents (<i>d</i>¹ synthon) and DDs as α-electrophiles (<i>a</i>² synthon) of carbonyl compounds open the way to two important classes of pyrazole compounds

Useful Access to Uncommon Thiazolo[3,2‑<i>a</i>]indoles

A practical and environmentally benign protocol for the assembly of poly substituted-thiazolo[3,2-a]indoles from 3-alkylated indoline-2-thiones and 2-halo-ketones has been developed. This metal-free approach consists in a complete chemo/regioselective formal [3 + 2] annulation that occurs in air, at 60 °C, and in water as the sole reaction medium. The opportunity to vary the substitution pattern up to six different positions, odorless manipulation of sulfurylated compounds, very easy product isolation, and mild reaction conditions are the main synthetic features of this method. The scaled-up experiment and the successive transformations of the products further demonstrate the utility of this chemistry

Synthesis of Densely Functionalized 3a,4-Dihydro‑1<i>H</i>‑Pyrrolo[1,2‑<i>b</i>]Pyrazoles via Base Mediated Domino Reaction of Vinyl Malononitriles with 1,2-Diaza-1,3-dienes

A domino reaction of vinyl malononitriles (VMs) with 1,2-diaza-1,3-dienes (DDs) produce unprecedented 3a,4-dihydro-1<i>H</i>-pyrrolo[1,2-<i>b</i>]pyrazole systems in a chemo-, regio-, and stereoselective fashion. This base promoted (DIPEA) one-pot transformation involving multiple steps constructs one new C–C bond, two C–N bonds, and two new fused heterocyclic rings with total atom economy

Tandem Aza-Wittig/Carbodiimide-Mediated Annulation Applicable to 1,2-Diaza-1,3-dienes for the One-Pot Synthesis of Fully Substituted 1,2-Diaminoimidazoles

One-pot sequential aza-Michael, Staudinger, and aza-Wittig reactions on 1,2-diaza-1,2-dienes (DDs) can afford fully substituted 1,2-diaminoimidazoles. A plausible mechanism for the imidazole core formation involving an intramolecular ring closure of the carbodiimide-derived phosphazene intermediate is given. The reported strategy has sufficient flexibility to allow substituted 1,2-diaminoimidazoles with orthogonal nitrogen-protective groups to be generated from a variety of heterocumulene moieties linked to the DDs skeleton

Powerful Approach to Heterocyclic Skeletal Diversity by Sequential Three-Component Reaction of Amines, Isothiocyanates, and 1,2-Diaza-1,3-dienes

By highly efficient, one-pot, three-component reactions, combining one set of 1,2-diaza-1,3-dienes (DDs), primary amines, and isothiocyanates in a different sequential order of addition, heterocyclic skeletal diversity can be achieved. The key feature discriminating the different heterocyclic core formation is the availability of the <i>N</i> or <i>S</i> heteronucleophile to give the first Michael addition step affording regioselective substituted 2-thiohydantoins or 2-iminothiazolidinones. The hydrazone or enehydrazino side chain at the 5-position of both heterocycles represents a valuable functionality to reach novel 5-hydroxyethylidene derivatives difficult to obtain by other methods

Interceptive [4 + 1] Annulation of in Situ Generated 1,2-Diaza-1,3-dienes with Diazo Esters: Direct Access to Substituted Mono‑, Bi‑, and Tricyclic 4,5-Dihydropyrazoles

In situ derived acyclic and cyclic 1,2-diaza-1,3-dienes (DDs) were engaged in interceptive [4 + 1] annulation strategy with diazo esters (DEs). The catalytic activity of inexpensive copper­(II) chloride allows the direct synthesis of mono-, bi-, and tricyclic 4,5-dihydropyrazole-5-carboxylic acid derivatives in a process that circumvents the use of an anhydrous and inert atmosphere

Divergent Approach to Thiazolylidene Derivatives: A Perspective on the Synthesis of a Heterocyclic Skeleton from β‑Amidothioamides Reactivity

Herein we report a domino protocol able to reach regioselectively thiazolylidene systems by combining the reactive peculiarities of both β-amidothioamides (ATAs) and 1,2-diaza-1,3-dienes (DDs). Depending on the reaction conditions and/or the nature of the residue at C4 of the heterodiene system, ATAs can act as hetero-mononucleophiles or hetero-dinucleophiles in the diversified thiazolylidene ring assembly