A solid-state [2 + 2] photodimerization involving coordination of Ag(I) ions to 2-pyridyl groups

Abstract

Photoreactive Ag(I) complexes of p-toluenesulfonate ions with the unsymmetrical alkene trans-1-(4-acetoxyphenyl)-2-(2-pyridyl)ethylene 1 is reported. The crystal [Ag(p-tol)(1)₂]?(H₂O) (p-tol?=?p-toluenesulfonate) undergoes a [2?+?2] photocycloaddition reaction in quantitative yield to afford the head-to-tail (ht) photoproduct rctt-1,3-bis(2-pyridyl)-2,4-bis(4-acetoxyphenyl)cyclobutane 2 regioselectively. The aromatic rings of the olefin participate in face-to-face π–π interactions and adopt an anti-conformation to position the carbon–carbon double bonds (C?=?C) in a suitable orientation to undergo photoreaction between neighboring complexes.     

Concise [4+3] cycloaddition reaction of pyrroles leading to tropinone derivatives

A concise [4+3] cycloaddition reaction of pyrroles with 2-(silyloxy)allyl cations has been developed. The oxyallyl cations stabilized with a methylthio group or geminal methyl groups were generated from the corresponding allylic alcohols under the influence of a Brönsted acid (Tf₂NH), respectively. The use of N-nosyl-protected pyrroles as the four-carbon unit was found to give tropinone derivatives in high yield.     

Cerium(IV) oxide as a neutral catalyst for aldehyde-induced decarboxylative coupling of l-proline with triethyl phosphite and nitromethane

The application of cerium(IV) oxide (CeO₂) as a neutral and heterogeneous catalyst for aldehyde-induced decarboxylative coupling of l-proline with triethyl phosphite and nitromethane is described. In addition, a [3+2] cycloaddition reaction of the in situ generated 1,3-dipolar intermediate with benzaldehyde in the absence of a nucleophile is also reported.     

Synthesis of optically active seven-membered 1,5-anhydrocarbasugars and 1,4,5-tribenzoyloxy-2-ethoxy cycloheptanes via [5+2] cycloaddition

[5+2] Cycloaddition followed by asymmetric dihydroxylation procedure have been utilized to prepare novel cyclitols. Accordingly, rac-2α-hydroxy-6α-ethoxy-1,5-anhydro cyclohept-3-ene, 10 derived from [5+2] cycloaddition of 3-oxidopyrylium ylide and vinyl ether has been recognized as a seven-membered carbasugar equivalent and elaborated to 1,4,5-tribenzoyloxy-2-ethoxy cycloheptanes through a flexible, regio- and stereoselective strategy involving Sharpless asymmetric dihydroxylation conditions to resolve the compounds obtained. The structures and relative configurations of newly synthesized (+)-2α-acetoxy-6α-ethoxy-3β,4β-dihydroxy-1,5-anhydro cycloheptane ((+)-12)); (−)-1β,4β,5β-tribenzoyloxy-6α-ethoxy cycloheptane ((−)-17) and (+)-1α,4α,5α-tribenzoyloxy-6β-ethoxy cycloheptane ((+)-17) are unambiguously established by single crystal X-ray analysis and duly supported by ¹H and ¹³C NMR spectroscopy data.     

乙烯亚胺与亚胺[2+2]环加成反应的理论研究

在ＨＦ／６－３１Ｇ和ＨＰ２／６－３１Ｇ站对乙烯亚胺和亚胺两模型分子的〔２＋２〕环加成反应的三种环加成方式进行了理论探讨。计算发现,环加成方式（１）和环加成方法（２）反应途径的位垒较低,反应较易进行;而环加成方式（３）位垒较高,反应较难发生。我们用前线轨道理论对其机理进行了初步探讨。     

二氟亚烷基卡宾与甲醛环加成反应机理的理论研究

用二阶微扰理论研究单重态二氟亚烷基卡宾与甲醛发生的环加成反应机理,采用MP2/6-31G^*方法计算了势能面上各驻点的构型参数、振动频率和能量.结果表明,单重态二氟亚烷基卡宾与甲醛的环加成反应主要有两种反应通道,通道1中,两个反应物经a,b和c三条反应途径生成三元环构型的产物P1,其中途径c是主反应途径,该途径有两步组成:(Ⅰ)二氟亚烷基卡宾与甲醛生成了1个富能中间体(INT1c),是无势垒放热反应,放出能量为219.18kJ/mol;(Ⅱ)中间体(INT1c)异构化为产物二氟亚烷基环氧乙烷,其势垒为134.71kJ/mol.通道2的反应途径由三步组成:(Ⅰ)反应物首先生成了1个富能中间体(INT1b),为无势垒的放热反应,放出的能量142.77kJ/mol;(Ⅱ)中间体(INT1b)异构化成另一中间体(INT2),其势垒为22.31kJ/mol;(Ⅲ)中间体(INT2)异构化成四元环构型产物P2,其势垒为11.98kJ/mol.     

A lifetime journey into the world of chemistry

The professional life of the author has been a fascinating journey through the magnificent landscapes of synthetic organic chemistry. A friendly editor invited him to share a few of these travel memories. This review is thus a (very) personal and (totally) prejudiced account of the author's research in organic chemistry. It describes the work of his associates and coworkers at UCLouvain in Belgium or at IECB in France. All schemes only deal with work which was done in both research groups. The names of the coworkers will appear in the references. The author apologizes to those coworkers whose work has not been cited but he had to sail within his pages' allocation. As will be seen, many areas of organic synthesis have been visited. The results of the research were put into perspective with the status of the field when the research was undertaken. Obviously several of these fields of research have dramatically expanded later on; credit could not be given here to these important developments. However, when available, some recent reviews will be cited to give a flavour of the most recent work. Thus, the reader should not expect to read a “classical” review of a topical subject. The purpose of this paper is merely the sharing of professional experiences of a modest but enthusiastic teacher and researcher.     

Cycloaddition of Alkenes and Alkynes to the P-centered Singlet Biradical [P(μ-NTer)]2

The reaction of biradical [P(μ-NTer)]₂ ( 1 , Ter = 2,6-bis(2,4,6-trimethylphenyl)phenyl) towards different alkenes (R = 2,3-dimethyl–butadiene, 2,5-dimethyl-2,4-hexadiene, 1,7-octadiene, 1,4-cyclohexadiene) and alkynes (R = 1,4-diphenyl-1,3-butadiyne) was studied experimentally. Although these olefins can react in different ways, only [2+2] cycloaddition products ( 1R ) were observed. The reaction with 2,3-dimethylbutadiene also led to the [2+2] product ( 1dmb ). Thermal treatment of 1dmb above 140 °C resulted in the recovery of biradical 1 upon homolytic bond cleavage of the two P–C bonds and the release of 2,3-dimethylbutadiene. In contrast to this reaction, all other [2+2] additions products ( 1R , R = 1,7-octadiene, 1,4-cyclohexadiene, 1,4-diphenyl-1,3-butadiyne) began to decompose at temperatures between 200 °C and 300 °C. Only unidentified products were obtained but no temperature-controlled equilibrium reactions were observed. Computations were carried out to shed light into the formal [2+2] as well as the possible [4+2] addition reaction.     

Intramolecular [4+2] cycloaddition reactions of indolylalkylpyridazines: synthesis of annulated carbazoles

Mono- and bicyclic 1,2-diazines tethered to indole dienophiles by alkylene chains were found to undergo thermally induced intramolecular Diels-Alder reactions with inverse electron demand, affording tetra- and pentacyclic condensed carbazoles.     

Synthesis of aryl- and hetarylpyrazoles

Hetaryldieneamines (1) react with sulfonyl azides to give 3-hetarylpyrazoles (5). Similarly, N,N-dimethyl-4-phenyldieneamine-2-carboxylic acid methyl ester (6) affords 3-phenylpyrazole-5-carboxylic acid methyl ester (7).

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Synthese von Aryl- und Hetarylpyrazolen (Kurze Mitteilung)

Zusammenfassung Reaktion von Hetaryldienaminen (1) mit Sulfonylaziden führt zu 3-Hetarylpyrazolen (5). N,-N-Dimethyl-4-phenyldienamin-2-carbonsäure-methylester liefert dabei 3-Phenylpyrazol-5-carbonsäure-methylester.