Automatic absolute determination of total sulfur by combustion and coulometric titration

An automatic method for the absolute determination of total sulfur, which overcomes the tendency of previous methods to give low sulfur recoveries on samples with high oxygen demand, is described. The technique combusts the sample in oxygen and sweeps the combustion gases through a hydrogen peroxide trap to remove the sulfur oxides from the gas stream. The trap contents are volatilized and swept with nitrogen through reduced copper heated to 890 °C. Sulfur oxides are quantitatively converted to sulfur dioxide and titrated coulometrically with iodine. Halogens are held by the copper and do not interfere with the sulfur determination. Analysis time is 12 min and automation of the method allows unattended operation. Sample size is 0.5 to 20 mg. Sulfur levels of 0.05 to 100% can be determined.     

The schmidt reaction on 3a,4,5,6-tetrahydrosuccinimido[3,4-b]-acenaphthen-10-one and its alkylated derivatives

The rearrangement of 3a,4,5,6-tetrahydrosuccinimido[3,4-b]acenaphthen-10-one and two methylated derivatives using Schmidt conditions is described. The ratio of the major product, 2,3,8,9-tetrahydro-3-oxo-1H-benz[de]isoquinoline-1,9a-(7H)dicarboximide, to the minor product, 2,3,6,7-tetrahydro-3-oxo-4H-benz[ij]-isoquinoline-4,4a-(5H)dicarboximide, under different acidic conditions is given. The ratios of analogous products from the methylated derivatives are similar under similar conditions.     

Intermolecular rhodium-catalyzed [2+2+2] carbocyclization reactions of 1,6-enynes with symmetrical and unsymmetrical alkynes

The crossed intermolecular rhodium-catalyzed [2+2+2] carbocyclization of carbon and heteroatom tethered 1,6-enynes can be accomplished with symmetrical and unsymmetrical alkynes, to afford the corresponding bicyclohexadienes in an efficient and highly selective manner.