Asymmetric Annulation of Donor–Acceptor Cyclopropanes with Dienes

Desymmetrization of 1-Symmetrical Donor-Acceptor (D-A) Cyclopropanes via Reactions with 1,3-Cyclodiones

A new type of 1-unsymmetrical D-A cyclopropanes containing a cyclic enone motif was obtained by the desymmetrization of 1-symmetrical D-A cyclopropanes via first the Lewis acid-catalyzed O-nucleophilic ring-opening reaction with 1,3-cyclodiones followed by an organobase-promoted unexpected multistep intramolecular transformation.

Recent Advances in Transition-Metal-Catalyzed (4+3)-Cycloadditions

A (4+3)-cycloaddition combines a four-atom synthon and three-atom synthon to form seven-membered rings. In the past decade, many improvements have been made to this class of cycloaddition, including excellent diastereo- and enantioselectivities, both intra- and intermolecularly. Through the strategic use of transition-metal catalysts, acids, bases, and organocatalysts, it is possible to perform the cycloaddition on a variety of substrates, generating novel seven-membered rings. With these advances, (4+3)-cycloaddition has also been applied to the synthesis of biologically relevant compounds and natural products. We exclude the cycloadditions of cyclic dienes such as furan, pyrrole, cyclohexadiene or cyclopentadiene as Chiu, Harmata, Mascareñas­ and others have recently published thorough reviews on that topic. We will however discuss the recent additions (2009–2020) to the literature for the (4+3)-cycloadditions involving other types of four-atom synthons.

1 Introduction

2 Rhodium

2.1 Cyclopropanation/Cope Rearrangement

2.2 C–H activation

3 Gold, Silver

4 Copper

5 Palladium, Platinum, Iridium

6 Dual-Activation

7 Conclusion

Cooperative Catalysis for the Highly Diastereo- and Enantioselective [4+3]-Cycloannulation of ortho-Quinone Methides and Carbonyl Ylides

We describe herein a highly diastereo- and enantioselective [4+3]-cycloannulation of ortho-quinone methides and carbonyl ylides to furnish functionalized oxa-bridged dibenzooxacines with excellent yields and stereoselectivity in a single synthetic step. The combination of rhodium and chiral phosphoric acid catalysis working in concert to generate both transient intermediates in situ provides direct access to complex bicyclic products with two quaternary and one tertiary stereogenic centers. The products may be further functionalized into valuable and enantiomerically highly enriched building blocks.

Photo/N-Heterocyclic Carbene Co-catalyzed Ring Opening and γ-Alkylation of Cyclopropane Enal

An unprecedented photo/NHC-co-catalyzed ring-opening C-C bond cleavage of cyclopropane enal and the following γ-alkylation with a halogenated compound via radicals were established, affording the corresponding γ-alkylated α,β-unsaturated esters in moderate to good yields.

Synthesis of novel polyethers with abundant reactive sites and diverse skeletons based on the ring-opening reaction of D–A cyclopropanes

Based on the ring-opening reaction of D–A cyclopropanes, a facile synthesis of novel polyethers is developed with molecular weights up to 17.7 kg mol⁻¹.

Lewis acid catalysed asymmetric cascade reaction of cyclopropyl ketones: concise synthesis of pyrrolobenzothiazoles

A concise method to synthesize pyrrolobenzothiazoles via a cascade reaction of cyclopropyl ketones was developed by using a chiral N,N′-dioxide-scandium(iii) complex catalyst.

Ring-opening reactions of donor–acceptor cyclopropanes with cyclic ketals and thiol ketals

Cyclic (thiol) ketals were used as hetero-nucleophiles for the ring opening of donor–acceptor cyclopropanes to afford functionalized diethers.

Brønsted acid mediated intramolecular cyclopropane ring expansion/[4 + 2]-cycloaddition

A cascade reaction of 3-hydroxy-2-phenylisoindolin-1-one and cyclopropyl ketone has been developed via a BrØnsted acid-promoted ring-opening/intramolecular cross-cycloaddition/[4 + 2]-cycloaddition process. The developed methodology provides straightforward access to pentacyclic isoindolin-1-one derivatives under simple reaction conditions.

Donor-Acceptor Cyclopropanes in the Synthesis of Carbocycles

Donor-acceptor cyclopropanes not only participate in a broad range of ring openings with nucleophiles, electrophiles, radical and red-ox agents, but also are excellent substrates for various (3+n)-cycloaddition and (3+n)-annulation processes. Moreover, under treatment with Lewis acid donor-acceptor cyclopropanes can produce new ring systems via isomerization or cyclodimerization. Authors' contribution to the synthesis of diverse carbocycles from donor-acceptor cyclopropanes is summarized in this account.

Ring-Opening 1,3-Aminochalcogenation of Donor-Acceptor Cyclopropanes: A Three-Component Approach

A 1,3-aminothiolation was realized by reacting 2-substituted cyclopropane 1,1-dicarboxylates with sulfonamides and N-(arylthio)succinimides. Under Sn(OTf)2 catalysis the transformation proceeded smoothly to the corresponding ring-opened products bearing the sulfonamide in the 1-position next to the donor and the arylthio residue in the 3-position next to the acceptor. The procedure was extended to the corresponding selenium analogues by employing N-(phenylseleno)succinimides as an electrophilic selenium source.

Stereospecific Copper(II)-Catalyzed Tandem Ring Opening/Oxidative Alkylation of Donor-Acceptor Cyclopropanes with Hydrazones: Synthesis of Tetrahydropyridazines

Aerobic copper(II)-catalyzed tandem ring opening and oxidative C-H alkylation of donor-acceptor cyclopropanes with bisaryl hydrazones is accomplished to produce tetrahydropyridazines, in which copper(II) plays dual role as a Lewis acid as well as redox catalyst. The reaction is stereospecific, and optically active cyclopropanes can be reacted with high optical purities (89-98% enantiomeric excess). The substrate scope, functional group tolerance, dual role of the copper(II) catalyst, and the use of air as an oxidant are the important practical features. A product bearing a 3-bromoaryl group can be subjected to Pd-catalyzed Suzuki coupling with boronic acid in high yield.

Stereospecific assembly of tetrahydroquinolines via tandem ring-opening/oxidative cyclization of donor-acceptor cyclopropanes with N-alkyl anilines

An aerobic copper-catalyzed tandem reaction of N-alkyl anilines with donor-acceptor cyclopropanes is presented for the construction of tetrahydroquinolines via a sequential stereospecific ring opening and oxidative cyclization. The catalyst plays a dual role as a Lewis acid as well as being a redox catalyst. The use of air as an oxidant and the broad substrate scope are the important practical features.

Brønsted Acid-Catalyzed (4 + 3) Cyclization of N, N'-Cyclic Azomethine Imines with Isatoic Anhydrides

A Brønsted acid-catalyzed (4 + 3) cyclization of N, N'-cyclic azomethine imines with isatoic anhydrides has been discovered, which constructs seven-membered nitrogenous heterocyclic frameworks with overall high yields (up to 98% yield). This reaction represents a rarely reported (4 + 3) cyclization of N, N'-cyclic azomethine imines, which involves the reassembly of a C-N bond. In addition, this reaction has also accomplished the unprecedented (4 + 3) cyclization of isatoic anhydrides.

Thiourea participation in [3+2] cycloaddition with donor–acceptor cyclopropanes: a domino process to 2-amino-dihydrothiophenes

The Yb(OTf)₃ catalyzed [3+2] cycloaddition of donor–acceptor cyclopropanes with thiourea offers an efficient route to diverse 2-amino-4,5-dihydrothiophenes.

Asymmetric ring-opening of cyclopropyl ketones with β-naphthols catalyzed by a chiral N,N′-dioxide–scandium(iii) complex

An efficient asymmetric ring-opening reaction of cyclopropyl ketones with 2-naphthols has been realized using a chiral N,N′-dioxide–Sc^III complex catalyst. A variety of chiral β-naphthol derivatives were obtained in excellent outcomes (up to 99% yield, 97% ee).