Cyclobutane

About: Cyclobutane is a research topic. Over the lifetime, 3106 publications have been published within this topic receiving 56747 citations.

Efficient visible light photocatalysis of [2+2] enone cycloadditions.

Abstract: We report that Ru(bipy)3Cl2 can serve as a visible light photocatalyst for [2+2] enone cycloadditions. A variety of aryl enones participate readily in the reaction, and the diastereoselectivity in the formation of the cyclobutane products is excellent. We propose a mechanism in which a photogenerated Ru(bipy)3+ complex promotes one-electron reduction of the enone substrate, which undergoes subsequent radical anion cycloaddition. The efficiency of this process is extremely high, which allows rapid, high-yielding [2+2] cyclizations to be conducted using incident sunlight as the only source of irradiation.

Structure and Function of DNA Photolyase

Abstract: Cyclobutane pyrimidine dimers (Pyr Pyr) are the major DNA photoproducts induced by the UV component of solar radiation. Photoreactivating enzyme (DNA photolyase) repairs DNA by utilizing the energy of visible light to break the cyclobutane ring of the dimer. Photolyases are monomeric proteins of 50-60 kDa with stoichiometric amounts of two noncovalent chromophore/cofactors. One of these cofactors is FADH-, and the second chromophore is either methenyltetrahydrofolate (MTHF) or 8-hydroxy-5-deazariboflavin (8-HDF). The enzyme binds the DNA substrate in a light-independent reaction, the second chromophore of the bound enzyme absorbs a visible photon and, by dipole-dipole interaction, transfers energy to FADH- which, in turn, transfers an electron to Pyr Pyr in DNA; the Pyr Pyr- splits and back electron transfer restores the dipyrimidine and the functional form of flavin ready for a new cycle of catalysis.

CRC handbook of organic photochemistry and photobiology

Abstract: Photochemistry Cis-Trans Isomerization of Alkenes, J. Saltiel, D.F. Sears, Jr., D.-H. Ko, and K.-M. Park Photorearrangement and Fragmentation of Alkenes, P.J. Kropp (2+2)-Cyclobutane Synthesis (Liquid Phase): Introduction and Mechanistic Consideration, G. Kaupp Cyclobutane Synthesis in the Solid Phase: Introduction and Mechanistic Considerations, G. Kaupp Photochemical Synthesis of Cage Compounds: Propellaprismanes and their Precursors, R. Gleiter and B. Treptow Copper(I) Catalyzed Intra- and Intermolecular Photocycloaddition Reactions of Alkenes, K. Langer and J. Mattay Photoreactions of Alkenes in Protic Media, P.J. Kropp The p-Cyclopropene Rearrangements, H.E. Zimmerman Diene/Cyclobutene Photochemistry, W.J. Leigh Photochemistry of Acyclic 1,3,5-Trienes and Related Compounds, W.H. Laarhoven and H.J.C. Jacobs Photochemistry of Vitamin D and Related Compounds, H.J.C. Jacobs and W.H. Laarhoven Photochemistry of Polyenes Related to Vitamin A, R.S.H. Liu Fulgides and Related Systems, H.G. Heller The Di-p-Methane Rearrangement, H.E. Zimmerman Photorearrangements of Benzobarrelenes and Related Analogues, C.-C. Liao and P.-H. Yang The Photochemistry of Dibenzobarrelene (9,10-Ethenoanthracene) and its Derivatives, J.R. Scheffer and J. Yang Valence Isomerization Between Norbornadiene and Quadricyclane Derivatives-A Solar Energy Storage Process, K. Maruyama and Y. Kubo Ring Isomerization of Benzene and Naphthalene Derivatives, A. Gilbert Phototransposition and Photo-Ring Contraction Reactions of 4-Pyrones and 4-Hydroxypyrylium Cations, J.W. Pavlik Photochemical Aromatic Substitution, J. Cornelisse Photochemical Reactions of Arenes with Amines, N.J. Bunce Intra- and Intermolecular Cycloadditions of Benzene Derivatives, P.A. Wender and T.M. Dore Cyclization of Stilbene and its Derivatives, A. Gilbert Ene Reactions with Singlet Oxygen, A.G. Griesbeck Photooxygenation of 1,3-Dienes, W. Adam and A.G. Griesbeck Photorearrangement of Endope roxides, J. Rigaudy Photochemical Methods for the Synthesis of 1,2-Dioxetanes, A.L. Baumstark and A. Rodriguez Oxidation of Aromatics, A. Albinia and M. Freccero Cyclobutane Photochemistry, K. Mizuno and C. Pac Photochemistry of Oxiranes - Photoreactions of Epoxynaphthoquinones, K. Maruyama and Y. Kubo Photodecarboxylation of Acids and Lactones, P. Wan and D. Budac The Photochemistry of Esters of Carboxylic Acids, J.A. Pincock Carbene Formation in the Photochemistry of Cyclic Ketones, S.M. Roberts Norrish Type I Processes of Ketones: Basic Concepts, C. Bohne Norrish Type I Processes of Ketones: Selected Examples and Synthetic Applications, C. Bohne Photoinduced Intermolecular Hydrogen Abstraction Reactions of Ketones, M. Rubin Hydrogen Abstraction Reactions of a-Diketones, M. Rubin Norrish Type II Photoelimination of Ketones: Cleavage of 1,4-Biradicals Formed by y-Hydrogen Abstraction, .J.-P. Wagner Norrish

The biology of the (6-4) photoproduct.

Abstract: The (6-4) photoproduct is an important determinant of the lethal and mutagenic effects of UV irradiation of biological systems. The removal of this lesion appears to correlate closely with the early DNA repair responses of mammalian cells, including DNA incision events, repair synthesis and removal of replication blocks. The processing of (6-4) photoproducts and cyclobutane dimers appears to be enzymatically coupled in bacteria and most mammalian cell lines examined (i.e. a mutation affecting the repair of one lesion also often affects the other), although exceptions exist in which repair capacity may be evident for one photoproduct and not the other (e.g. UV61 and the XP revertant cell line). These differences in the processing of the two photoproducts in some cell lines of human and rodent origin suggest that in mammalian cells, different pathways for the repair of (6-4) photoproducts and cyclobutane dimers may be used. This observation is further supported by pleiotropic repair phenotypes such as those observed in CHO complementation class 2 mutants (e.g., UV5, UVL-1, UVL-13, and V-H1). Indirect data, from HCR of UV irradiated reported genes and the cytotoxic responses of UV61, suggest that the (6-4) photoproduct is cytotoxic in mammalian cells and may account for 20 to 30% of the cell killing after UV irradiation of rodent cells. Cytotoxicity of the (6-4) photoproduct may be important in the etiology of sunlight-induced carcinogenesis, affecting mutagenesis as well as tumorigenesis. The intricate photochemistry of the (6-4) photoproduct, its formation and photoisomerization, is in itself extremely interesting and may also be relevant to sunlight carcinogenesis. The data reviewed in this article support the notion that the (6-4) photoproduct and its Dewar photoisomer are important cytotoxic determinants of UV light. The idea that the (6-4) photoproduct is an important component in the spectrum of UV-induced cytotoxic damage may help clarify our understanding of why rodent cells survive the effects of UV irradiation as well as human cells, without apparent cyclobutane dimer repair in the bulk of their DNA. The preferential repair of cyclobutane dimers in essential genes has been proposed to account for this observation (Bohr et al., 1985, 1986; Mellon et al., 1986). The data reviewed here suggest that understanding the repair of a prominent type of noncyclobutane dimer damage, the (6-4) photoproduct, may also be important in resolving this paradox.

The application of cyclobutane derivatives in organic synthesis.

Abstract: I. Introduction 1485II. Scope of This Review 1485III. Transformations of Cyclobutane Derivatives inOrganic Syntheses1486A. Ring-Opening Reactions 1486B. Ring-Contraction Reactions 1493C. Ring-Expansion Reactions 14951. Five-Membered Rings 14952. Six-Membered Rings 15093. Seven-Membered Rings 15174. Eight-Membered Rings 15215. Nine-Membered Rings 1523IV. Transformations of Cyclobutane Derivatives inNatural Product Syntheses1524A. Ring-Opening Reactions 1524B. Ring-Expansion Reactions 15261. Five-Membered Rings 15262. Six-Membered Rings 15293. Seven-Membered Rings 15324. Eight-Membered Rings 1533V. Conclusion 1534VI. Acknowledgments 1534VII. References 1534