No abstract

not afford the expected dimer l 4 of tri-tert-butylcyclobutadiene. Rather, the exclusive product in essentially quantitative yield was cyclopropenyl ketone 6.The fact that 6 was also formed from the solvolysis of 1 suggests that cationic intermediate^'^ may be involved in the oxidation of 2 as well. Details of the mechanism of this latter transformation remain obscure at the present time. Efforts to provide information in this area are in progress.Acknowledgments. Acknowledgment is made to the Research Corporation for financial support of this work. We thank Mr. J. G. Henkel for the use of his computer program and Mr. S. Cichanowski for the dipole moment determination. (14) We have obtained a compound which possesses the expected analytical and spectroscopic data for a dimer of tri-tert-butylcyclobutadiene, namely 1,3,4,5,7,8-hexa-tert-butyltricyclo[4.2.O,O~~~]octa-3,7diene (IO) by reaction of 1 with lithium amalgam in ether. This dimer may be formed by a stcpwise double Wurtz reaction. Cf. discussion in ref 6.

Glycoside Coupling of Protected Daunosamine to Diol 26b. A stirred solution of 326 mg (0.60 mmol) of 2,3,6-trideoxy-l,4di-O-p-nitrobenzoyl-S-trifluoroacetamido-a-L-Zyxo-hexopyranose17 in 10 mL of dry CH2C12 at 0 °C under argon was treated with gaseous HC1 for 3 min. After standing at 25 °C for 10 min, the p-nitrobenzoic acid was removed by filtration and the filtrate was concentrated to dryness yielding 200 mg (ca. 100%) of glycosyl chloride 31. The chloro sugar (0.60 mmol), diol 26b (140 mg, 0.44 mmol), and powdered anhydrous CaC03 (200 mg, 2.0 mmol) were vigorously stirred in 10 mL of dry CH2C12 under argon while a solution of 154 mg (0.60 mmol) of silver trifluoromethanesulfonate (AgTF) in 5 mL of dry THF was added over a 5-min period. The diol appeared to dissolve and the mixture darkened as addition of AgTf progressed. After stirring for 15 min at 25 °C, TLC (40% EtOAc/hexane) showed two mobile products, Rf 0.50 and R¡& 0.42 with only a trace of starting diol remaining. The reaction mixture was filtered and filtrate was dried over Na2S04. Concentration in vacuo gave 450 mg of a light brown foam. Preparative TLC on eight 20 cm X 20 cm (0.5 mm) silica gel plates with 25% EtOAc/hexane gave 75 mg of isomer A and 60 mg of isomer B. Both isomers gave similar spectra which indicated some decomposition upon chromatography. Isomer A was purified by precipitation from CH2C12 with hexane:

No abstract

ti on is energetically more favorable due to the lower charge repulsion to be overcome.Research in progress is directed toward determining the scope of the method, particularly its applicability to more highly saturated molecules and to the synthesis of carcinogenic aromatic hydrocarbons and related compounds otherwise accessible only through tedious multistep procedures.