Rh(III)-Catalyzed Dual C–H Functionalization/Cyclization Cascade by a Removable Directing Group: A Method for Synthesis of Polycyclic Fused Pyrano[de]Isochromenes

Abstract

An interesting Rh­(III)-catalyzed dual C–H functionalization/cyclization cascade of azomethine imine with diazophosphonate by a removable directing group for the synthesis of highly fused pyrano­[de]­isochromene has been achieved. The transformation shows that the desired pyrano­[de]­isochromenes with two oxygen atoms on its core scaffold could be constructed with good to excellent yields (up to 86%) via a facile one-pot, multiple-step cascade reaction, along with broad generality and versatility.

Comprehensive Review on Synthesis, Properties, and Applications of Phosphorus (PIII, PIV, PV) Substituted Acenes with More Than Two Fused Benzene Rings

“…Shu et al [ 82 ] described a new synthetic method for the preparation of 2-hydroxy-1-(dimethoxyphosphoryl)anthracene 188 in the reaction of an imine derivative of azomethine 189 and dimethyl diazophosphonate 190 in the presence of inorganic additives ( Scheme 72 ). The reaction was carried out at 100 °C and the compound 188 was obtained in a 29% yield.…”

Ru(ii)-catalyzed synthesis of indolo[2,3-c]isoquinolines via [3+3] annulation of N,N′-cyclic azomethine ylides and 3-diazoindolin-2-imines

“…12 Shu and co-workers have performed [3+3] annulation of N,N 0 -cyclic azomethine ylides and diazophosphonates to yield polycyclic fused pyrano[de]isochromenes. 13 In continuation of our earlier efforts at developing novel synthetic strategies, 14 we have developed a [3+3] annulation approach for the construction of indolo[2,3-c]isoquinoline frameworks from N,N 0 -cyclic azomethine ylides and 3-diazoindolin-2-imines employing a Ru(II) catalyst in the current work. The ability of N,N 0 -cyclic azomethine ylides to serve as removable directing groups (DGs), with the removal of DG occurring in situ and followed by carrying out an annulation, has already been described by Cheng and co-workers, and a similar observation was found in our work during the preliminary screenings for the reaction.…”

“…12 Shu and co-workers have performed [3+3] annulation of N , N ′-cyclic azomethine ylides and diazophosphonates to yield polycyclic fused pyrano[ de ]isochromenes. 13…”

Sulfoximines Assisted Rh(III)-Catalyzed C–H Activation/Annulation Cascade to Synthesize Highly Fused Indeno-1,2-benzothiazines

“…Direct use of the diazo substrate containing only carbonyl groups without further preactivation as the coupling partners seems to offer a more facile pathway to construct diversified heterocycle scaffolds, but very few examples involving all-carbon diazo substrates as coupling partners have been reported to construct complicated fused polycyclic scaffolds . In continuation of our interest in the development of highly effective synthetic methods to construct a diverse drug-like heterocyclic compound library by Rh­(III)-catalyzed C–H bond activation strategies, we surprisingly found that we could easily obtain an interesting highly fused indeno-1,2-benzothiazine scaffold by a sulfoximine directed C–H activation/annulation cascade using an all-carbon diazo indandione as the coupling partner (Scheme c). More importantly, this strategy is the first to use the more simple unactivated diazo indandione as the coupling partner to construct fused tetracyclic indeno-1,2-benzothiazines with high efficiency, broad substrate generality, and further transformation potential.…”