A Domino-Based Approach toward Stereodefined Heavily Functionalized Cyclohexanes:  Synthesis of Iridal's Core Structure

Abstract

A stereoselective synthesis of heavily functionalized six-membered ring subunits, which possess functionality at sites appropriate for further elaboration, is described. The cyclopentanone moiety of hydrindenediol is required to achieve total facial selectivity during the pre-domino installation of the second quaternary center, while oxidative cleavage is responsible for the ring-expanding rearrangement. A microwave-assisted version of the key domino transformation and a test of concept approach toward the iridal core structure are also presented.

Microwave-assisted domino reactions: function-compatibility, modulation, and greening efforts

“…1 All experiments were run in triplicate, and agreement was generally within less than 10%. Yields are an average of three runs, not optimized.…”

“…In a preliminary communication, 1 we showed that a variety of cyclohexane derivatives possessing adjacent quaternary carbons can be prepared by a three-step procedure using a Pb(OAc) 4 mediated hetero-domino reaction 2 as a key construction step (Scheme 1). 3 The starting hydrindene-diols of type-1 can be readily assembled and constitute attractive precursors for highly elaborated type-3 or 6 cyclohexanes, type-4 bridged bicyclic systems, and type-5 fused -bicyclic lactones.…”

Cytotoxic iridal-type triterpenoids from Iris tectorum

“…8 Various biological activities of these substances including cytotoxicity, [9][10] ichthyotoxicity, 11 antiplasmodial, 12 and PKC activation 13 have been reported, making them attractive targets for chemical synthesis. [14][15][16] In our continuing search for new bioactive iridals, 5 seven new iridals (1)(2)(3)(4)(5)(6)(7) were isolated from the ethanol extract of rhizomes of I. tectorum, together with three known analogues (8)(9)(10). We report herein the isolation, structure elucidation and cytotoxic activities of these compounds (Fig.…”

Stimulating excursions into organolead chemistry: modular domino sequences triggered by oxidative cleavage

“…These results were then used for comparison with the microwave assisted domino process results. 70 A quick screen of potential solvents was carried out to identify a solvent that would be suitable for assisting the microwave heating. Although a poor solvent for microwave irradiation, toluene was initially tested as it had been utilized previously for the domino transformations.…”