Diarylcarbene preparation

Dimesitylcarbene, prepared by the photolysis of dimesityldiazomethane, is unique amongst the diarylcarbenes thus far investigated in that its triplet state... 

In an effort to produce diarylcarbenes with singlet ground states rather than the more usual triplet ground states, the diazoparacyclophane derivatives (49) were prepared and irradiated. Triplet signals were detected spectroscopically for three of the five carbenes (50) studied, but no definite conclusions could be drawn regarding the multiplicities of these ground states. 

Aryl and diarylcarbenes are easily prepared by irradiation of the corresponding diazo-compounds. Topics studied include the... 

In the following sections the methods used to prepare cyclopropanes by addition of aryl-and diarylcarbenes to alkenes are presented. Most mechanistic aspects of the methods have been dealt with in detail by Wentrup reaction mechanisms will, therefore, be not discussed in detail. 

Diarylcarbene complexes of transition metals are considerably less reactive toward alkenes than the analogous monoarylcarbene complexes and, therefore, have been little used for preparation of gew-diarylcyclopropanes. Some examples, however, have been reported. When a solution of pentacarbonyldiphenylmethylidenetungsten in ethyl vinyl ether was heated to 37 °C for 3 hours, l-ethoxy-2,2-diphenylcyclopropane (2) was obtained in 61% yield together with 1,1-diphenylethene (3) and 2-ethoxy-l,l-diphenylethene If the reaction is carried in... 

A large variety of gem-diarylcyclopropanes have been prepared by the addition of diarylcarbenes to alkenes and other substrates containing C-C double bonds. The number of precursors and methods that have been employed to perform the preparations are, however, rather limited compared to the abundance of methods available for the synthesis of monoarylcyclo-... 

Various diarylcarbenes, whose aryl groups belong to a polycyclic, aromatic system, react with a number of alkenes and form spirocyclopropanearenes. Such carbenes are generally prepared by thermal and photochemical decomposition of the corresponding diazo compounds. Other... 

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