Synthesis Of Cyclobutanes Research Articles

Photoredox‐Catalyzed Cyclobutane Synthesis by a Deboronative Radical Addition–Polar Cyclization Cascade

AbstractPhotoredox‐catalyzed methylcyclobutanations of alkylboronic esters are described. The reactions proceed through single‐electron transfer induced deboronative radical addition to an electron‐deficient alkene followed by single‐electron reduction and polar 4‐exo‐tet cyclization with a pendant alkyl halide. Key to the success of the methodology was the use of easily oxidizable arylboronate complexes. Structurally diverse cyclobutanes are shown to be conveniently prepared from readily available alkylboronic esters and a range of haloalkyl alkenes. The mild reactions display excellent functional group tolerance, and the radical addition‐polar cyclization cascade also enables the synthesis of 3‐, 5‐, 6‐, and 7‐membered rings.

Stereoselective Synthesis of Cyclobutenes via Nickel Catalysis

Stereoselective Synthesis of Cyclobutenes via Nickel Catalysis

Photoredox-Catalyzed Cyclobutane Synthesis by a Deboronative Radical Addition-Polar Cyclization Cascade.

Photoredox‐catalyzed methylcyclobutanations of alkylboronic esters are described. The reactions proceed through single‐electron transfer induced deboronative radical addition to an electron‐deficient alkene followed by single‐electron reduction and polar 4‐exo‐tet cyclization with a pendant alkyl halide. Key to the success of the methodology was the use of easily oxidizable arylboronate complexes. Structurally diverse cyclobutanes are shown to be conveniently prepared from readily available alkylboronic esters and a range of haloalkyl alkenes. The mild reactions display excellent functional group tolerance, and the radical addition‐polar cyclization cascade also enables the synthesis of 3‐, 5‐, 6‐, and 7‐membered rings.

Cobalt‐Catalyzed Reductive Coupling of Alkynes and Acrylates Bearing a Leaving Group: Construction of Cyclobutene Rings

AbstractThis study reports a cobalt‐catalyzed synthesis of cyclobutenes using alkynes and acrylates bearing a leaving group at the α position. The cyclobutene formation was facilitated by an appropriate proton source. In the presence of a Lewis acid, acetonitrile participated in the reaction, affording the corresponding functionalized cyclobutenes.

From Straightforward Gold(I)-Catalyzed Enyne Cyclizations to more Demanding Intermolecular Reactions of Alkynes with Alkenes

Gold(I) complexes are the catalysts of choice for the selective activation of alkynes in the presence of other unsaturated functional groups. In this Account, we present the development of gold(I)-catalyzed intermolecular reactions of terminal alkynes with functionalized alkenes. In particular, we focus on the synthesis of cyclobutenes by asymmetric gold(I)-catalyzed [2+2] cycloaddition and its applications.1 Introduction2 Intramolecular Gold(I)-Catalyzed Synthesis of Cyclobutenes2.1 Role of Cyclobutenes in 1,n-Enynes Cycloisomerizations2.2 [2+2] Cycloaddition of 1,n-Enynes3 Intermolecular Gold(I)-Catalyzed Reactions of Terminal Alkynes with Alkenes3.1 [2+2] Cycloaddition of Alkynes with Alkenes3.2 Reactions of Propiolic Acid with Alkenes3.3 [2+2+2] Cycloaddition of Alkynes with Oxoalkenes3.4 Reaction of Alkynes with Furanes4 Gold(I)-Catalyzed Enantioselective Synthesis of Cyclobutenes5 Concluding Remarks

Synthesis of Cyclobutenes via a Palladium-Catalyzed Asymmetric Heck Reaction

Synthesis of Cyclobutenes via a Palladium-Catalyzed Asymmetric Heck Reaction

Catalytic asymmetric synthesis of a nitrogen heterocycle through stereocontrolled direct photoreaction from electronically excited state

The reactivity of photoexcited molecules has been extensively studied for decades but until today direct bond-forming reactions of such excited states in a catalytic and asymmetric fashion are restricted to the synthesis of cyclobutanes via [2 + 2] photocycloadditions. Herein, we demonstrate a previously elusive visible-light-induced catalytic asymmetric [2 + 3] photocycloaddition of alkenes with vinyl azides. A wide range of complex 1-pyrrolines are obtained as single diastereoisomers and with up to >99% enantiomeric excess using a simple reaction setup and mild reaction conditions. The reaction is proposed to proceed through the photoexcitation of a complex out of chiral rhodium catalyst coordinated to α,β-unsaturated N-acylpyrazole substrates. All reactive intermediates remain bound to the catalysts thereby providing a robust catalytic scheme (no exclusion of air necessary) with excellent stereocontrol. This work expands the scope of stereocontrolled bond-forming reactions of photoexcited intermediates by providing catalytic asymmetric access to a key nitrogen heterocycle in organic chemistry.

ChemInform Abstract: Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

AbstractReview: 853 refs.

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions.

The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 20 years (i.e., from 1995 to 2015). Organization of the data follows a subdivision according to mechanism and substrate classes. Cu(I) and PET (photoinduced electron transfer) catalysis are treated separately in sections 2 and 4, whereas the vast majority of photocycloaddition reactions which occur by direct excitation or sensitization are divided within section 3 into individual subsections according to the photochemically excited olefin.

Synthesis of Cyclobutanes by Lewis Acid-Promoted Ketene-Alkene [2+2] Cycloadditions

Synthesis of Cyclobutanes by Lewis Acid-Promoted Ketene-Alkene [2+2] Cycloadditions

ChemInform Abstract: Synthesis of Cyclobutenes and Allenes by Cobalt‐Catalyzed Cross‐Dimerization of Simple Alkenes with 1,3‐Enynes.

Cobalt-catalyzed cross-dimerization of simple alkenes with 1,3-enynes is reported. A [2+2] cycloaddition reaction occurred, with alkenes bearing no allylic hydrogen, by reductive elimination of a η(3)-butadienyl cobaltacycle. On the other hand, aliphatic alkenes underwent 1,4-hydroallylation by means of exo-cyclic β-H elimination. These reactions can provide cyclobutenes and allenes that were previously difficult to access, from simple substrates in a highly chemo- and regioselective manner.

ChemInform Abstract: Retrospective View on Recent Developments in Cyclobutane Synthesis via [2 + 2] Photocycloaddition of Unsaturated Ketones to Acyclic Dienes

AbstractReview: 24 refs.

Retrospective View on Recent Developments in Cyclobutane Synthesis via [2+2] Photocycloaddition of Unsaturated Ketones to Acyclic Dienes

AbstractThis synopsis addresses cyclobutane formation via light‐induced [2+2] cycloaddition from both cyclic and acyclic unsaturated carbonyl compounds, and 2,3‐dimethylbuta‐1,3‐diene

Synthesis of cyclobutenes and allenes by cobalt-catalyzed cross-dimerization of simple alkenes with 1,3-enynes.

Cobalt-catalyzed cross-dimerization of simple alkenes with 1,3-enynes is reported. A [2+2] cycloaddition reaction occurred, with alkenes bearing no allylic hydrogen, by reductive elimination of a η(3)-butadienyl cobaltacycle. On the other hand, aliphatic alkenes underwent 1,4-hydroallylation by means of exo-cyclic β-H elimination. These reactions can provide cyclobutenes and allenes that were previously difficult to access, from simple substrates in a highly chemo- and regioselective manner.

Applications of C-H functionalization logic to cyclobutane synthesis.

The application of C–H functionalization logic to target-oriented synthesis provides an exciting new venue for the development of new and useful strategies in organic chemistry. In this article, C–H functionalization reactions are explored as an alternative approach to access pseudodimeric cyclobutane natural products, such as the dictazole and the piperarborenine families. The use of these strategies in a variety of complex settings highlights the subtle geometric, steric, and electronic effects at play in the auxiliary guided C–H functionalization of cyclobutanes.

Enantioselective Synthesis of Cyclobutanes via Sequential Rh-catalyzed Bicyclobutanation/Cu-catalyzed Homoconjugate Addition

Enantiomerically enriched cyclobutanes are constructed by a three-component process in which t-butyl (E)-2-diazo-5-arylpent-4-enoates are treated with Rh2(S-NTTL)4 to provide enantiomerically enriched bicyclobutanes, which can subsequently engage in homoconjugate addition/enolate trapping sequence to give densely functionalized cyclobutanes with high diastereoselectivity. This three-component, two-catalyst procedure can be carried out in a single flask. Rh2(S-NTTL)4-catalyzed reaction of t-butyl (Z)-2-diazo-5-phenylpent-4-enoate gives the Büchner cyclization product in excellent enantioselectivity.

Asymmetric Synthesis of Cyclobutanes by a Formal [2+2] Cycloaddition Controlled by Dienamine Catalysis

Trap it: A combination of aminocatalysis with H-bonding activation is used in two new approaches to carry out formal enantioselective organocatalyzed [2+2] cycloaddition reactions. This cooperative catalysis solves the inconveniences associated with this transformation. These two new reactions will open opportunities to find reactivities involving other organocatalytic cycloadditions.

ChemInform Abstract: Synthesis of Cyclobutenes by [2+2]‐Cycloaddition Reaction

AbstractReview: 45 refs.

Stereoselective preparation of cyclobutanes with four different substituents: total synthesis and structural revision of pipercyclobutanamide A and piperchabamide G.

A general strategy was developed for the diastereo- and enantioselective synthesis of cyclobutanes with four different substituents. It consists of three transition metal-catalyzed reactions — a RhII-catalyzed cyclopropanation, a AgI-catalyzed regioselective and stereospecific ring expansion, and a RhI-catalyzed addition reaction. Structures of pipercyclobutanamide A and piperchabamide G were synthesized and revised.

ChemInform Abstract: Chiral Cyclobutane Synthesis by Exploiting a Heteroatom‐Directed Conjugate Addition.

AbstractStarting from D‐arabinal derivative (I), a synthesis of epoxide (II) is developed and its reaction with various carbon nucleophiles is studied.