Szeimies

Szeimies RM, Gerritsen MJ, Gupta G, Ortonne JP, Serresi S, Bichel J, Lee JH, Fox TL, Alomar A (2004) Imiquimod 5% cream for the treatment of actinic keratosis results from a phase III, randomized, double-blind, vehicle-controlled, clinical trial with histology. J Am Acad Dermatol 51 547-555... 

Szeimies recently published an impressive example of a steric effect on a Sr2 reaction at carbon for the addition of thiols to the central bond of bicyclo[ 1.1.0]-systems87. From the radical chain addition of thiophenol to 32 the stereoisomeric cyclobutanes 33a and 33b are obtained exclusively in 56% yield. The thiylradical... 

Hans Peter Reisenauer Wolfram Sander Gunter Szeimies... 

Chloro-2-(chloromethyl)-1-propene is commercially available but is very expensive (> 45/g for 10 g, Aldrich Chemical Company, 1996). It is commonly used in the synthesis of natural products,5 polymers,6 cryptands and crown ethers,7 compounds of biological and medical importance,8 and is the starting material for the Szeimies synthesis of [1.1.1]propellane.9... 

Wiberg and Waddell also noted that propellane reacts with iodine in 88% yield.2 Alber and Szeimies report a somewhat lower yield (61%) when an ethereal solution of propellane is treated with a solution of iodine in ether/pentane while being irradiated.3 Thus, titration of a portion of the resulting propellane solution with iodine provides an estimate of the minimum yield. A 3.0-mL portion of the propellane solution is transferred as noted above. Small pieces of iodine are added with stirring under room light over 10 min until just before the dark color persists. Concentration of the... 

The synthesis of [1.1.1]propellane from 1 is essentially as reported by Michl and co-workers,10 with only a slight modification in the process of transferring the crude propellane solution. As a result of the submitters improvements in the preparation of 3-chloro-2-(chloromethy)propene4 and 1,1-dibromo-2,2-bis(chloromethyl)cyclO propane, many of the difficulties in the Szeimies route to [1.1,1]propellane have been eliminated. 

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