Seyferth’s method

Chemical Modification. Reactions on the macromolecular polyenes were carried out by procedures described previously (3, 4). PhHgCBr3 is obtained by a modification of Seyferth s method (21) from PhHgBr and HCBr3 in presence of a base. Yields similar to those reported in the literature are obtained more easily by replacing the complex (tert-BuOK— tert-BuOH) with a solution of sodium tert-amylate in benzene as prepared by Conia (24). This reagent was, in fact, used systematically in place of potassium tertf-butylate it is easier to use and can be prepared completely free of alcohol. 

The products C are obtained by reduction of products B (X = Br) by Seyferth s method using Bu3SnH at 80°C. (24). This conversion gives yields of more than 95% in the presence of an excess of hydride. The same reaction with B (X = Cl) at 140°C. only results in the reduction of one halogen by using other reagents such as Ph3SnH the same result is obtained, but lower temperatures are possible (i.e., about 100°C.). 

The results of the syntheses of a number of stannylcyclopropanes can be found in refs 148, 234, 235, 568-570. Most compounds have been prepared by stannylation of the lithiocyclo-propanes formed when 1,1-dibromocyclopropanes are treated with butyllithium at — 100 °C (Seyferth s method).Generally, the compounds are formed in a nonstereospecific fashion in reasonable yield, for example, stannylation of 7,7-dibromobicyclo[4.1.0]heptane to give 1 and of oxazole 2 to give... 

Cyclopropenes. Chan and Massuda have prepared cyclopropenes by fluoride ion-promoted elimination of trimethylhalosilane from dihalocarbene adducts of vinylsilanes. Thus 1-chlorocyclopropene (3) was prepared from trimethylvinylsilane (1) by addition of dichlorocarbene (Seyferth s method, 1, 852). Elimination of trimethylchlorosilane was effected with cesium fluoride... 

Based on the extensive work of Harrod and coworkers , Seyferth and coworka-s also examined metallocene (i.e. Cp2ZrH2) catalyzed dehydrogenative crossUnking of PMS as another method of increasing ceramic yields and carbon content during transformation... 

Phosphinylmethylstannanes. Ethereal 1.73 M methyllitium added at room temp, under Ng to a slurry of triphenylphosphine oxide in ether, and the resulting soln. containing diphenylphosphinylmethyllithium allowed to react with triphenyltin chloride diphenylphosphinylmethyltriphenylstannane. Y 76%.— This simple method provides a convenient route to organofunctional phosphine oxides and sulfides from the readily available triphenylphosphine oxide and sulfide. F. e., also thiophosphinylmethyl derivatives, s. D. Seyferth, D. E. Welch, and J. K. Heeren, Am. Soc. 85, 642 (1963). 

A mixture of p-fluorophenylmercuric bromide and dicobalt oclacarbonyl in tetrahydrofuran allowed to react 1 hr. at room temp, under Ng 4,4 -difluoro-benzophenone. Y 93%. - This is a general method for the prepn. of sym. ketones from easily accessible startg. m. under mild conditions. A non-hydro-lytic work-up is used with removal of excess cobalt carbonyl by triphenyl-phosphine. F. e. s. D. Seyferth and R. J. Spohn, Am. Soc. 90, 540 (1968). 

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