Addition of carbenes and

The Addition of Carbenes and Carbenoids to Double and Tripie Bonds... 

This section deals with transformations of heterocyclic rings and includes not only addition of carbenes and nitrenes, but also rearrangements frequently following these additions. Also included are topics such as the synthesis of Reissert compounds as well as miscellaneous oxidations and reductions. 

The simplest example of a 2 + 2 addition about which there is substantial information would appear to be the addition of carbenes and nitrenes to olefins (Equations 12.4 and 12.5). Woodward and Hoffmann have designated reactions of this kind, in which one component is a single atom, as cheleotropic.5... 

Relative Reactivities of Some Olefins towards Addition of Carbenes and Carbenoids in Solution... 

Tertiary phosphines (especially triphenylphosphine) react with various compounds giving rise to the formation of alkylidenephosphoranes. " By the addition of carbenes and carbenoids, respectively, to tertiary phosphines especially, alkylidenephosphoranes are available which carry one or two halogen atoms at the a-carbon atom (equation 1). 

The addition of carbenes and carbenoids to imines and nitriles continues to be a popular approach to aziridines and 2//-azirines. These processes have been well reviewed by Deyrup (B-83MI101-01). Dichlorocarbene and other dihalocarbenes have been added to a wide variety of imines to provide dihaloaziridines. A recent example is shown in Equation (64), illustrating the use of phase-transfer conditions <93H(36)69i). The treatment of azides with excess dichlorocarbene results in the formation of the 2,2,3,3-tetrachloroaziridines (92TL2339). Presumably, the azide is converted by dichlorocarbene to the imidoyl dihalide RN=CC12 which reacts further with dichlorocarbene. Transition metal-promoted reaction of a-diazoesters with imines provides 2-(alkoxycarbonyl)aziridines [Pg.46]

Methylenecyelopropanes also undergo reactions characteristic for reactive olefines, such as electrophilic additions, radical additions, additions of carbenes and nitrenes as well as the various other types of cycloadditions (Scheme 3). 

Synjanti Product Ratios in Cyclopropanes Obtained by the Addition of Carbenes and Carbenoida to Olefins... 

Addition of Carbenes and Carbene Precursors to Aromatic Hydrocarbons and to Fullerene[60]... 

Addition of Carbenes and Carbenoids to Olefins.— The addition of carbenes and carbenoids to olefins provides a standard method for the synthesis of cyclopropanes and much of the current work is concerned with the provision of new carbene sources and the improvement of procedures. 

No mechanisms have been reported for these postulates by the authors. The reaction in Equation 5.1 would, however, require fluorine rearrangement in the 1,4-biradical that intermediates OFCB formation, and the reaction in Equation 5.2 would require the simultaneous addition of carbene and rearrangement of fluorine in the 1,3-biradical which would form from the reaction of Tre and CF2. 

Addition of Carbene and Carbenoids to Olefins.—The addition of carbenes and carbenoids to olefins continues to be one of the most popular routes used for cyclopropane synthesis. A review of carbenes (and nitrenes) based on the 1973 literature has appeared during the year, and methoxycarbonyl carbene has been the subject of a theoretical study. ... 

Dibromocarbene generated under phase-transfer conditions inserts into the a-C-H bond of ( -l,3-hexadiene)Fe(CO)3 to give (74) a similar reaction occurs with (chd)Fe(CO)3. Diazomethane reacts with triene (75) to give (76) on oxidation with Ce +, nitrogen extrusion to yield the cyclopropane derivative occurs, in addition to decomplexation. Reaction of (75) with the sulphur ylide (CH3)2 S=CHC02Me proceeds similarly to give (77).Methods for the addition of carbene and dichlorocarbene to the unco-ordinated double bonds of (cot)Fe(CO)3 and (chpt)Fe(CO)3 have been described. 

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