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Carbon monoxide diradical

Thiirane 1,1-dioxides extrude sulfur dioxide readily (70S393) at temperatures usually in the range 50-100 °C, although some, such as c/s-2,3-diphenylthiirane 1,1-dioxide or 2-p-nitrophenylthiirane 1,1-dioxide, lose sulfur dioxide at room temperature. The extrusion is usually stereospeciflc (Scheme 10) and a concerted, non-linear chelotropic expulsion of sulfur dioxide or a singlet diradical mechanism in which loss of sulfur dioxide occurs faster than bond rotation may be involved. The latter mechanism is likely for episulfones with substituents which can stabilize the intermediate diradical. The Ramberg-Backlund reaction (B-77MI50600) in which a-halosulfones are converted to alkenes in the presence of base, involves formation of an episulfone from which sulfur dioxide is removed either thermally or by base (Scheme 11). A similar conversion of a,a -dihalosulfones to alkenes is effected by triphenylphosphine. Thermolysis of a-thiolactone (5) results in loss of carbon monoxide rather than sulfur (Scheme 12). [Pg.141]

Diazomethane when heated with copper powder gives nitrogen and an insoluble polymethylene, indicating that one of its reactions is the decomposition into methylene radicals. The methylene radical can also be formed in the gas phase and detected by a mirror experiment.81 The pyrolysis of ketene in the gas phase gives carbon monoxide and methylene radical. The methylene radical both reacts with itself to give ethylene and removes tellurium mirrors, forming tellurform-aldehyde.82 Thus the methylene diradical(P) behaves as expected. [Pg.45]

Zewail and his co-workers addressed this question in their laboratory and studied the stability of the tetramethylene diradical generated from various precursors in real time. He showed with femtosecond spectroscopy that intermediate product was in fact formed and had a lifetime of 700 fs. Using cyclopentanone as the precursor they have shown that with two photons at 310 nm (pump) carbon monoxide is eliminated through an a-cleavage. [Pg.82]

Of mechanistic interest in this context is the independent generation of di-ir-methane diradicals of 3-oxa-di-TT-methane systems which do not give the rearrangement, in order to probe whether such diradicals at least in principle are prone to give di-ir-methane products. For this purpose, the cyclopropyldicarbinyl diradical in equation (25) was generated via photochemical carbon monoxide extrusion. Indeed, the expected oxa-di-ir-methane product 2,5-dimethyl-4,5-epoxy-2-hexene was formed, as well as other products. [Pg.201]

A variety of methods are used to generate and study diyls including, to name a few, the thermal or photochemically promoted extrusion of nitrogen from a pyr-azoline, the Norrish type I photochemically initiated extrusion of carbon monoxide from a cyclic ketone, and the Bergman cyclization of enediynes [3-5]. In this chapter we focus upon the synthetic utility of diradicals, paying particular attention to the work of others as well as research originating from our laboratory. [Pg.881]

Aldehydes show an elimination reaction (loss of carbon monoxide, CO), that is not possible with ketones. Butanal, for example, photodissociates to propane and carbon monoxide. Cyclic ketones dissociate to a diradical (41 from cyclopentanone), which then reacts in any of several ways including elimination to ethene or 42 and coupling to cyclobutane. Formation of cyclobutane and ethene is accompanied by expulsion of CO prior... [Pg.1156]

Organometallic reagents were used for the synthesis of bicyclic aromatic compounds via Moore-type cyclization. Rahm and Wulff described the new synthesis of 5-hydroxyindolines with the use of a chromium carbene complex bearing alkynyl substituent 22." The amino-tethered bis-alkynyl carbene complex 22 was transformed into indoline 23 by thermolysis in the presence of a hydrogen source. The low yield of product 23 was improved when the reaction was carried out in the presence of the electrophile, added to protect the phenol function. This process involves the insertion of one carbon monoxide group from the chromium complex into the skeleton of an eneyne compound 24. The resulting enyne-ketene 25 undergoes a cycloaromatization reaction to afford the 1,4-diradical intermediate 26. Subsequent demetalation yields product 23."... [Pg.360]

Photo-decarboxylation Acyclic carbonyl diradical on decarboxylation give carbon monoxide, an alkene or a cyclic alkane or both. [Pg.263]


See other pages where Carbon monoxide diradical is mentioned: [Pg.150]    [Pg.369]    [Pg.392]    [Pg.397]    [Pg.399]    [Pg.190]    [Pg.36]    [Pg.174]    [Pg.2052]    [Pg.430]    [Pg.499]    [Pg.995]    [Pg.2051]    [Pg.276]    [Pg.195]    [Pg.275]    [Pg.275]   
See also in sourсe #XX -- [ Pg.15 , Pg.102 ]




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