Boron Trifluoride‐Promoted Indium(III) Triflate‐Catalyzed Sequential One‐Pot Synthesis of (1,2‐Diaryl‐2‐oxoethyl)malonates from trans‐2‐Aryl‐3‐nitrocyclopropane‐1,1‐dicarboxylates and Activated Arenes

Abstract

A sequential one‐pot synthesis of Michael adducts of aroylmethylidenemalonates with activated aromatics is described. The method involves treatment of trans‐2‐aryl‐3‐nitro‐cyclopropane‐1,1‐dicarboxylates with boron trifluoride etherate to form aroylmethylidenemalonates in situ and then addition of activated aromatics such as indoles, carbazole, pyrrole, thiophenes, methoxybenzenes and benzodioxole followed by a catalytic amount of indium(III) triflate to the same reaction vessel. To prove the synthetic potential of the resulting Michael adducts, one of the adducts was transformed into a pharmaceutically interesting dihydropyridazinone derivative.

Synthetic Applications of Aroyl‐ and Nitro‐substituted 2‐Aryl‐Cyclopropane‐1,1‐Dicarboxylates

“…Taking clues from the above observations, we have also developed a sequential one‐pot synthesis of Michael adducts of aroylmethylidene malonates with activated aromatics 13 (Scheme ) . Accordingly, the treatment of nitrocyclopropanes 2 with BF 3 .OEt 2 generated aroylmethylidene malonates 9 in situ .…”

First synthesis of acylated nitrocyclopropanes

“…For example, when esters 1a are subjected to Lewis acid-induced denitration, highly electron-deficient enones (reaction b) [ 4 ] are obtained. The latter compounds are highly reactive and undergo reaction with, e.g., mercaptoacetaldehyde affording thiophenes (reaction c) [ 5 ] or with activated (hetero)aromatic compounds to give diarylated (oxoalkyl)malonates [ 6 ]. In the reaction using tin(II) chloride as the Lewis acid, the ring opening and nucleophilic attack of the nitro group occur, to produce functionalized isoxazolines (reaction d) [ 7 ].…”

The Regioselective Functionalization Reaction of Unprotected Carbazoles with Donor–Acceptor Cyclopropanes

“…Srinivasan and co-workers described a Michael addition reaction of an arene with trans-2-aryl-3-nitrocyclopropane-1,1-dicarboxylates as the only substrate, affording the C3-functionalized carbazole in two steps (Scheme 1a). 15 Li and co-workers developed a rhodium-catalyzed C−H activation of (hetero)arenes with cyclopropanol, affording an alkylated carbazole as a unique example (Scheme 1b). 16 Obviously, the need for the installation and removal of a directing group and the requirement of more than one step greatly compromise the overall efficiency of the reaction.…”

“…Up to now, transformations related to carbazoles and cyclopropanes have been scarce. Srinivasan and co-workers described a Michael addition reaction of an arene with trans -2-aryl-3-nitrocyclopropane-1,1-dicarboxylates as the only substrate, affording the C3-functionalized carbazole in two steps (Scheme a) . Li and co-workers developed a rhodium-catalyzed C–H activation of (hetero)­arenes with cyclopropanol, affording an alkylated carbazole as a unique example (Scheme b) .…”