Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

Abstract

A novel and efficient approach to the synthesis of 2-vinylbenzylamines is reported. This involves obtaining 2-vinylbenzylamine ligands from tetrahydroisoquinoline by alkylation and reduction followed by the Hofmann cleavage. The resultant 2-vinylbenzylamines allowed us to obtain new Hoveyda–Grubbs catalysts, which were thoroughly characterised by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10−2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM).

Application of New Efficient Hoveyda–Grubbs Catalysts Comprising an N→Ru Coordinate Bond in a Six-Membered Ring for the Synthesis of Natural Product-Like Cyclopenta[b]furo[2,3-c]pyrroles

“…The third part of the work is related to the study of the catalytic activity of ruthenium catalysts 1 and 2 ( Figure 1 ) under the RRM protocol. According to the previous paper [ 27 ], the N , N -dimethyl catalyst 2 is the most thermally stable, while the morpholine derivative catalyst 1 is the most active (as it has the longest coordination N→Ru bond ~2.32 Å).…”

“…N,N-Dimethylamino derivative ( Cat. 2 ), with a shorter bond length between nitrogen and ruthenium (the N→Ru bond is 2.24 Å [ 27 ]), is stable at least up to 140 °C [ 27 ], and therefore turned out to be effective for the preparation of cyclopenta[ b ]furo[2,3- c ]pyrrole 7p at temperatures above 100 °C in microwave-assisted experiments (entries 17–26, Table 4 ). It should be noted that the amount of catalysts 1 and 2 required for the complete conversion of the initial esters 6eA , 6pA did not exceed 0.5 mol % in both cases, while the reaction time was much shorter than in the papers cited above [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ].…”

“…In regard to design of new catalysts for RRM, our group recently prepared a new class of effective ruthenium catalysts comprising an N→Ru coordinate bond in a six-membered ring (Cat.1 and Cat.2) (Figure 1) and found that they revealed a high level of activity (up to 10 −2 mol%) in standard models for the olefin metathesis (styrene, allylbenzene, diethyl diallylmalonate, diallyltosylamide, norbornen/hex-1-ene, etc.) [27,28]. for the olefin metathesis (styrene, allylbenzene, diethyl diallylmalonate, diallyltosylamide, norbornen/hex-1-ene, etc.)…”

“…for the olefin metathesis (styrene, allylbenzene, diethyl diallylmalonate, diallyltosylamide, norbornen/hex-1-ene, etc.) [27,28]. According to the statements above and with the knowledge that there are no reports on the efficient synthetic methods for diversely polyfunctionalized cyclopenta[b]furo [2,3-c]pyrroles using easily available 3-allyl-3a,6-epoxyisoindoles derived from 1-(furan-2-yl)-N-arylmethanimines through the intramolecular Diels-Alder furan (IMDAF) reaction, our research was focused on: (i) Establishing the optimal conditions for the diastereoselective preparation of 3-allyl-3a,6epoxyisoindoles, according to the variables: solvent, acid catalysts, reaction time and temperature; (ii) With the determined conditions in hand, preparing diverse 3a,6-epoxyisondol-7-carboxylic acids and their methyl esters; (iii) Corroborating the spatial structure of isomeric acids and their esters; (iv) Studying the catalytic activity of ruthenium catalysts 1 and 2 in the RRM of 3a,6-epoxyisoindole-7carboxylates in comparison with HG-II catalyst; and (v) With the established conditions in hand, preparing the desired cyclopenta[b]furo [2,3-c]pyrroles.…”

Transposition of Aromaticity from a Furan to a Cyclohexane Ring in Furoisoindoles During the Interaction of 3-(Furyl)allylamines with Bromomaleic Anhydride

“…As part of our research in the field of tandem acylation-[4+2]-cycloaddition reactions of ,-unsaturated acid anhydrides with vinylarenes (the intramolecular Diels-Alder reaction in vinylarenes -the IMDAV reaction) 7 and search for new original objects for metathesis reactions, 8 in this communication we used bromomaleic anhydride and 3-furylallylamines as starting materials for the construction of the furo[2,3-f]isoindole framework. It should be noted that, prior to our work, bromomaleic anhydride was used several times as an intramolecular dienophile.…”