Iridium‐Catalyzed Tandem Cyclization of Benzoylacetonitriles with Diazo Compounds Leading to Substituted Naphtho[1,8‐bc]pyrans by Sequential C−H Functionalization

Abstract

The cascade annulation reactions of benzoylacetonitriles with diazo compounds proceed efficiently in the presence of an iridium catalyst to give substituted naphtho [1,8-bc]pyrans by sequential cleavage of C(sp 2 )ÀH/C(sp 3 )ÀH and C(sp 2 )ÀH/ OÀH bonds. Interestingly, the reactions involving cyclic diazo compounds and open-chain diazo compounds lead to different types of naphtho [1,8bc]pyrans. Most products are obtained in moderate to good yields with a broad range of substrates.

Synthesis of Polysubstituted Phenols by Rhodium‐Catalyzed C−H/Diazo Coupling and Tandem Annulation

“…In addition, substrates of 1 with other electron withdrawing groups such as ester, nitro, trifluoromethyl and carbonyl groups are not effective substrates ( 3 ia – 3 ma ). The above data and related literature reports of us [21b] and other research groups [20b,c] show that the CN group may also serve as a coordination auxiliary group in addition to the electron withdrawing properties.…”

Free‐Amine‐Directed Iridium‐Catalyzed C−H Bond Activation and Cyclization of Naphthalen‐1‐amines with Diazo Compounds Leading to Naphtho[1,8‐bc]pyridines

“…In contrast Ir(III)‐catalyzed C−H activation reactions employing diazo compounds as coupling partners were reported not as much as Rh(III)‐catalyzed reactions. Following our growing interest in building heterocyclic compounds using diazo compounds, and iridium‐catalyzed C−H bond functionalizations, we herein report a free‐amine‐directed iridium‐catalyzed C−H bond activation and cyclization of naphthalen‐1‐amines with diazo compounds leading to naphtho[1,8‐ bc ]pyridines in mild conditions (Scheme c). Different from the previous free‐amine‐directed C−H functionalization with diazo compounds that relied on the coordination of lone pair electrons or in situ formation of imine, this reaction passes through a five‐membered iridacycle intermediate containing an N−Ir σ‐bond.…”

“…On the basis of known transition‐metal‐catalyzed C−H bond activation reactions and our group's related research,, a possible mechanism is proposed for this present catalytic reaction (Scheme ). The first step is likely to be a ligand exchange between [Cp*Ir(CH 3 CN) 3 ](SbF 6 ) 2 and HOAc to form the catalytic species [Cp*Ir(OAc)(MeCN)](SbF 6 ), which then coordinates with 1 a and subsequently occurs C( sp 2 )−H bond activation to form a five‐membered iridacycle intermediate A by releasing HOAc.…”

Transition Metal‐Catalyzed Intermolecular Cascade C−H Activation/Annulation Processes for the Synthesis of Polycycles

“…[39] Almost at the same time, Wang and co-workers disclosed as imilar access to substituted naphtho[1,8-bc]pyrans via iridium(III)-catalyzedt andemc yclization of benzoylacetonitriles with cyclic diazo compounds by using NaOAc and PivOH as additives (Scheme41). [79] Notably,w hen open chain diazo compounds were used with HOAc as additive, hydroxyl naphtho[1,8-bc]pyrans were constructed in a mixture of diastereomers. Experimental results indicated that C(sp 2 )ÀHb ond cleavage might be involved in the turnover-limiting step.…”