Synthesis of hybrid dendrimer-star polymers by the RAFT process

A first generation phosphorus-containing dendrimer with twelve terminal benzyl dithiobenzoate functions was designed and subsequently used as a multifunctional agent to derive hybrid star copolymers consisting of a dendritic core surrounded by twelve polystyrene branches by reversible addition-fragmentation chain transfer (RAFT).     

Column selectivity in reversed-phase liquid chromatography. VIII. Phenylalkyl and fluoro-substituted columns

As reported previously, five solute-column interactions (hydrophobicity, steric resistance, hydrogen-bond acidity and basicity, ionic interaction) quantitatively describe column selectivity for 163 alkyl-silica, polar-group and cyano columns. In the present study, solute retention and column selectivity for 11 phenyl and 5 fluoro-substituted columns were compared with alkyl-silica columns of similar ligand length. It is concluded that two additional solute-column interactions may be significant in affecting retention and selectivity for the latter columns: (a) dispersion interactions of varying strength as a result of significant differences in bonded-phase polarizability or refractive index and (b) pi-pi interactions in the case of phenyl columns and aromatic solutes. These 16 phenyl and fluoro columns were also characterized in terms of hydrophobicity, steric resistance, hydrogen-bond acidity and basicity, and ionic interaction.     

Relative coarse-graining

The problem of statistical inference based on a partial measurement (coarse-graining) requires the specification of an a priori distribution. We reformulate the ordinary theory such as to encompass systematically a wide range of a priori distributions (relative coarse-graining). This is done in a mathematical setting which admits an interpretation in both classical probability and quantum mechanics. The formalism is illustrated in a few simple examples, such as the die whose geometrical shape is known, the spin in thermal equilibrium with an unknown reservoir, and the position measurement of a one-dimensional particle. It is shown that some of the limitations of the usual theory are a consequence of the fact that it is restricted to equidistributed (symmetric) a priori states.     

Synthesis in the thienobenzoxazepine series. First synthesis of a diethienoxazepine

In an investigation of novel tricyclic systems, synthesis of several thieno[2,3-b][1,4]benzoxazepines and thieno[3,2-b][1,5]benzoxazepines were effected by ring closure of appropriately amino aldehyde compounds. A new oxazepine fused with two heterocyclic rings, the dithieno[3,2-b:2,3-f][1,4]oxazepine, is described.     

Ring-opening reactions of 3-substituted 1-azabicyclo[1.1.0]butane with dichlorocarbene

Reaction of 3-ethyl-1-azabicyclo[1.1.0]butane ( 1a ) with chloroform-potassium tert-butoxide afforded a ring-opened product, 1,1-dichloro-2-aza-4-ethylpenta-1,4-diene ( 4a ), which was characterized via conversion to the corresponding N-substituted 5-chloro-1,2,3,4-tetrazole, Sa . Reaction of 3-phenyl-1-azabicyclo-[1.1.0]butane ( 1b ) with “Seyferth's reagent” (PhHgCCl₂Br) afforded 1,1-dichloro-2-aza-4-phenylpenta-1,4-diene ( 4b ), which also was characterized via conversion to a tetrazole derivative, i.e., 5b . Finally, the reaction of 1b with dichlorocarbene generated under phase transfer conditions (chloroform-sodium hydroxide-TEBA) was studied. At short reaction times (0.5 hour), the major reaction product was 4b . However, at longer reaction times (20–30 hours), two secondary products, 8 and 9 , were formed which resulted via subsequent dichlorocyclopropanation of 4b .     

Unusual occurrence of photooxidation of a cage diol

An unusual photooxidation was noted upon photolytic cage closure of a substituted tricyclo[6.2.1.0^2.7]undecane-exo, exo-diol. The resultant compound, which may be regarded as a mono-reduced pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8,11-dione, was characterizedvia X-ray crystallography. This species could be reduced to the tricyclo[6.2.1.0^2,7]undecane-endo, exo-diol under conditions previously shown to be inert for the parent dione.     

2,8,10,11-tetrachloro-12-oxahexacyclo-[7.2.1.02,8.03,7.04,11.06,10]dodeca-1,9-diol and disorder and mixed crystals in a system of tetracyclo-[6.3.0.04,11.05,9]undecanone and undecanol derivatives

2,8,10,11-Tetrachloro-12-oxahexacyclo[7,2.1.0^2.8.0^3.7.0^4.11.0^6.10]dodeca-1,9-diol is a strained cage molecule containing six five-membered rings and a four-membered ring. Twenty-five of the internal angles are less than 105° with 6 ranging from 89.5(3) to 97.4(3)°. The base promoted reaction of 3,6-dipyridyl-1,2,4,5-tetrazine with tetracyclo[6.3.0.0^4.11.0^5.9]undecane-3,6-dione yields the monoketone 6,7-[3,6-di(2-pyridyl)-4,5-pyridizino]tetracyclo[6.3.0.0^4.11.0^5.9]-undecan-2-one. This compound crystallizes in the centrosymmetric space group P2₁/n with enantiomers related by a center of symmetry. In the crystal investigated the molecules are disordered with each site containing about 80% of one isomer and 20% of the enantiomer. When the ketone is hydrogenated and the product isolated, two different crystals were found to have a ratio of alcohol to ketone of .71/.29 and .75/.25 or about 3/1. The alcohol and ketone occupy the same sites, but with opposite stereochemistries.