Thietane Formation Research Articles

DAST-Mediated Fluorination of 1-[4-Thio-β-d-arabinofuranosyl]uracil: Investigation of Thiolane vs Thietane Formation and Stereoselective Synthesis of 4′-ThioFAC

AbstractThe unprecedented DAST-mediated (DAST = diethylaminosulfur trifluoride) deoxygenative fluorination of benzoyl-, TBDPS-, and Bn-protected 1-(β-d-4-thioarabinofuranosyl)uracil at the sugar portion was examined. Three kinds of nucleoside (Ns) products were formed: target thiolane Ns, ring-contracted thietane Ns, and anhydro Ns products. The reaction pathway was determined by the electronic effect of the protecting groups at the sugar and base moieties. The benzoylated uracil starting material gave the 2,2′-anhydronucleoside (anhydro Ns) as a major product, whereas the silylated and benzylated starting materials furnished the corresponding fluorinated products, in which the ring-contracted thietanes predominantly formed. The desired thiolane Ns could be obtained as major product by the addition of a pyridine derivative as an additive. Upon reacting N 3-benzoylated 1-(β-d-4-thioarabinofuranosyl)uracil with DAST in the presence of 2,4,6-collidine, the target 2′-deoxy-2′-β-fluoro-4′-thiouracil nucleoside could be obtained in 72% isolated yield along with the corresponding thietane Ns (7%) and anhydro Ns (3%) (thiolane Ns/thietane Ns/anhydro Ns = 10.3:1.00:0.43), with recovery of the starting material (12%). In this study, the first stereoselective synthesis of the β-anomer of 1-(2-deoxy-2-fluoro-4-thio-β-d-arabino-pentofuranosyl)cytosine (4′-thioFAC) has been developed.

Solid state photochemical reaction of achiral N-(β,γ-unsaturated carbonyl)thiocarbamate to optically active thiolactone in the chiral crystalline environment

O-Methyl N-(2,2-dimethylbut-3-enoyl)-N-phenylthiocarbamate crystallized in the chiral space group P21, and the solid state photoreaction initiated intramolecular [2+2] thietane formation followed by rearrangement, leading to optically active γ-thiolactone.

Absolute Asymmetric Synthesis from Achiral Molecules in the Chiral Crystalline Environment

AbstractThe current status of absolute asymmetric synthesis in a chiral crystalline environment has been reviewed. A number of topochemically controlled four‐center type photocycloadditions are described for a series of unsymmetrically substituted diolefin crystals and CT crystals. This concept has been applied to intramolecular photoreactions, and several successful absolute asymmetric syntheses have been achieved, involving Norrish Type II reaction, di‐π‐methane rearrangement, electrocyclization, thietane formation, oxetane formation, hydrogen abstraction by thiocarbonyl and alkenyl groups, and radical‐pair intermediates.

Thietane, tetrahydrothiophene and tetrahydrothiopyran formation in reaction of methylene-interrupted dienoates with dimethyl disulfide

The reaction of dimethyl disulfide in I 2 with a series of methylene-interrupted methyl dienoates was examined. In all cases ring-closure occurs and thietane formation competes favorably with tetrahydrothiophene formation. When the I 2 concentration was increased, tetrahydrothiopyran formation was observed. These results are explained in terms of two distinct reaction pathways.

Solid-State Photochemistry: Diastereoselective Synthesis of Thietane-Fused .beta.-Lactams from an Acyclic Monothioimide with a Chiral Group

Irradiation of N-[(R)-1-phenylethyl]-N-tigloythiobenzamide in benzene solution resulted in both [2+2] thietane and thioketone formation reactions (via β-hydrogen abstraction by the thiocarbonyl sulfur). Diastereoselectivity in the thietane formation was not observed, in that four β-lactams were obtained in similar yields. In contrast to the solution photochemistry, irradiation of the crystals provided remarkably high diastereoselectivities. At 15 o C, de of the syn-β-lactams was 61% and the ratio of syn/anti was to 8.7 (chemical yield: 78%). The solid-state photoreaction proceeded even at -78 o C, with higher diastereoselectivity. At low conversion (9%) only syn isomers (de=93%) were obtained, and 71% de was observed even at 90 % conversion. An X-ray crystal structure of the monothioimide indicates that the crystal is orthorhombic, of space group P2 1 2 1 2 1 , and the distances between the sulfur atom and the alkenyl carbon, and from the thiocarbonyl carbon to the alkenyl carbon, are 4.29 and 3.00 A, respectively. The twist angle τ of the C(=O)-N bond is 40.8° and that of the C(=S)-N bond is 19.9°. On the other hand, the sulfur atom and abstractable hydrogen atom are in close proximity, and the value for d is 2.40 A, for θ is 127.3°, for Δ is 67.9°, and for ω is 6.2°. From these values, it is apparent that this reactant is well-positioned for hydrogen transfer in the crystalline state

Novel Insight into the Stereochemical Pathway Leading to (6-4) Pyrimidine-Pyrimidone Photoproducts in DNA

Irradiation of the dinucleoside phosphate 5 led to three photoproducts which were fully characterized, the formation of thietane 9 provides evidence suggesting a novel minor pathway to “6-4” lesions in DNA.

A remarkable thietane formation from a 6-mercaptopurine derivative

An unusual rearrangement/thietane ring formation results from the treatment of an 3-chloro-2-hydroxypropyl iminothioether with base. 6-Oxo-1-(thietan-3-yl)-purine (3) was characterized by spectral analysis and conversion to thientanyl 5-amino-4-carboxamidoimidazole (6) whose structure was confirmed by x-ray analysis.

Photoreactions of thiobarbiturates with olefins; Thietane formation by intermolecular photocycloaddition.

Upon irradiation of thiobarbiturates (1a-c) in the presence of olefins (4a-d), [2+2]cycloaddition occurred to give thietanes (5, 7, and 8) and its related compounds (6 and 9).

Photochemistry of .alpha.,.beta.-unsaturated thiones. Cycloaddition to electron-deficient olefins from higher excited states

Electron-deficient olefins add to thioenone 1 upon m* excitation. Cycloaddition occurs to the thiocarbonyl chromophore preferentially from the less-hindered side to yield thietanes. Thietane formation is stereospecific and regioselective. This addition has been inferred to originate from the second excited singlet, S2(?rx*), state. The exciplex intermediacy has been inferred from the dependence of the fluorescence quenching rate constant on the electron-acceptor properties of the olefin. The observed site specificity and regioselectivity are rationalized on the basis of PMO theory. The observed photochemical behavior of thioenone is different from that of enones.

Lack of stereoselectivity in the formation of thietane 1,1‐dioxide derivatives from anancomeric aminocyclohexenes

AbstractTwo diastereoisomeric thietane 1,1‐dioxides are formed in the reaction of methanesulfonyl chloride with 4‐t‐butylcyclohexanone enamines in the presence of triethylaraine. Their structures and relative chemical stabilities are discussed.

Dependence of the optical induction on the mechanism of the photochemical thietane formation

The photochemical thietane formation from 3a and 1 or 5 proceeds with 3 to 4.5 times higher optical purity via the T 1 state of the thiones than via the S 2 state.

Stereochemistry of formation of thietane, thiolane and thiane derivatives in cyclisations of dichloro alcohols and chlorooxiranes

Stereochemistry of formation of thietane, thiolane and thiane derivatives in cyclisations of dichloro alcohols and chlorooxiranes

Mechanism of thietane formation from the reaction of 1,3-dioxan-2-ones with thiocyanate ion. Stereochemical investigation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of thietane formation from the reaction of 1,3-dioxan-2-ones with thiocyanate ion. Stereochemical investigationLeo A. Paquette and John P. FreemanCite this: J. Org. Chem. 1970, 35, 7, 2249–2253Publication Date (Print):July 1, 1970Publication History Published online1 May 2002Published inissue 1 July 1970https://doi.org/10.1021/jo00832a032RIGHTS & PERMISSIONSArticle Views221Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (718 KB) Get e-Alerts Get e-Alerts