Asymmetric Synthesis of Nature‐Inspired Bioactive Spiro Compounds through Organocatalytic Diels–Alder Reactions

Abstract

An asymmetric organocatalytic arylideneacetone-olefin[ 4 + +2] cycloaddition reactiono favarietyo fa rylideneacetones and 1,3-indandione with different aldehydes is reported in toluenea ta mbient conditions to furnish the optically pure spiro compounds, whicha re further converted into medicinally usefuls piromentins by the Suzukir eaction. This asymmetric reaction has advantageous features such as high rate ands electivity,u ses easily availables ubstrates/catalysts,h as many synthetic/ medicinal applications,a nd gives excellent yields for generating av ast libraryo fc hiral spiro compounds.

Unusual In‐Situ Preorganization and Postoxidation Steps Observed in Diels‐Alder Reactions of Styrylcyclohexene Dienes

“…The [4+2] cycloadditions of conjugated dienes to various types of multiple bonds, known for nearly one century as the Diels‐Alder (DA) reaction, [1] is perhaps the most practiced method for the construction of six‐membered rings in a single synthetic operation [2] . The ability of the reaction to form up to four stereogenic centers with predictable regiochemistry and absolute configuration, [3] combined with the ease of operation and convenient execution of chiral auxilaries [4] and catalysts [5] have facilitated successful applications of this pericyclic process in stereoselective synthesis of enantioenriched natural products, [6] biologically active compounds, [7] and desired complex molecular structures [8] . Employment of high pressure techniques [9] and Lewis acid mediated methods [10] along with the development of intramolecular, [11] transannular, [12] temporary tethered, [13] self‐assembled, [14] and hetero [15] variants of the reaction have further extended the scope of this remarkable process.…”

Crystal Structure, Thermodynamic Properties and DFT Studies of 5,6-dimethyl-1H-benzo[d]imidazol-3-ium 3-((2,4-dioxo-1,5-dioxaspiro[5.5]undecan-3-ylidene)methyl) -2,4-dioxo-1,5-dioxaspiro[5.5]undecane Hydrate

“…On the other hand, the bond angle of C8-C10-C11 in predicted values with the experimental ones is 132.30 • and 130.62(13) • , respectively, which is also similar to related structures reported(C15-C17-C9 131. 19(1) • ) [24]. The experimental torsion angles for C7-C8-C10-C11, C8-C10-C11-C12, C8-C10-C11-C14 and C9-C8-C10-C11 are 167.64 (14)…”

“…As other heterocyclic compounds, spiro compounds containing O heteroatom have also attracted much attention due to its special structure in recent years. All kinds of spirocyclic compounds were designed and synthesized [19][20][21]. Based on the above reasons, our group has prepared several spirocyclic compounds derived from the 1,5-dioxaspiro group or the 6,10-dioxaspiro group in ten years [22][23][24][25].…”

Unravelling the Development of Non-Covalent Organocatalysis in India

“…An unprecedented, highly efficient, asymmetric organocatalytic arylideneacetone–olefin [4+2] cycloaddition reaction of a range of arylideneacetones 217 and 1,3-indandione ( 219 ) with different aldehydes 218 to afford optically enriched spiro compounds 220 and 221 (minor) has been reported by Ramachary and co-workers (Scheme 73 ). 128 The reaction proceeds through a Barbas dienamine strategy with good yields and high exo -selectivity by adopting a synergistic combination of a Brønsted acid and a primary amine. The benefit of this protocol lies in the fact that it proceeds under ambient reaction conditions, utilises easily available substrates and the obtained optically pure spiro compounds can be further converted into spiromentins, which have pharmacological importance, via the Suzuki reaction.…”