Julia sets and periodic kneading sequences

We construct abstract Julia sets homeomorphic to Julia sets for complex polynomials of the form f _c (z) = z ² + c, having an associated periodic kneading sequence of the form [`(a*)]{\overline{\alpha\ast}} which is not a period n-tupling. We show that there is a single simply-defined space of “itineraries” which contains homeomorphic copies of all such Julia sets in a natural combinatorial way, with dynamical properties which are derivable directly from the combinatorics. This also leads to a natural definition of abstract Julia sets even for those kneading sequences which are not realized by any polynomial f _c , with similar dynamical properties.     

Practical routes to diacetylenic ketones and their application for the preparation of alkynyl substituted pyridines, pyrimidines and pyrazoles

Alkynyl substituted pyridines, pyrimidines and pyrazoles have been synthesised by cyclocondensations of diacetylenic ketones with enamines, amidines and hydrazines, respectively.     

Functionalisation of unactivated methyl groups through cyclopalladation reactions

The transformation of the organopalladium compound (3) into the corresponding deuteriated, chlorinated, or oxidized derivatives (7), (8), or (9), (11), and (12) respectively. is described. The palladation of compound (9) takes place regioselectively leading to the palladated system (13), which is transformed into the difunctionalised oximes (15) and (16). The palladation of $\text{E}$-2,2-dimethyl and 2,2,6,6-tetramethyl-cyclohexanone oxime leads to the corresponding organopalladium compounds (17) and (27), which through deuteriation or oxidation affords the expected products (21) and (31), or (22), (23), (24), and (32), respectively. The second palladation of the compound (22) takes place on the remaining methyl group yielding the organopalladium derivative (26). Finally, $\text{E}$-lupanone oxime is palladated selectively in the 23-position leading to the organopalladium compound (38); the transformation of this compound into its 23-deuterio and 23-acetoxy- derivatives (41) and (42), respectively is also described. The stereochemistry in the palladatlon of lupanone oxime is deduced from NOE studies at 500 MHz.     

Studies toward the total synthesis of the cytotoxic sponge alkaloid pyrinodemin A

[structure: see text]. The syntheses of the proposed structure of pyrinodemin A (1) and its cis double bond positional isomer (C15'-C16') in racemic form are described. The key reaction involved an intramolecular nitrone/double bond cycloaddition. Our results suggest that neither 1 nor its double positional isomer is the correct structure of pyrinodemin A     

Solution reduction synthesis of surface stabilized silicon nanoparticles

This paper describes the preparation of air and moisture stable octanol derivatized crystalline silicon nanoparticles by room temperature sodium naphthalenide reduction of silicon halides.     

Thermal isomerizations of cis,anti,cis-tricyclo[6.4.0.0]dodec-3-ene to trans- and cis,endo-tricyclo[6.2.2.0]dodec-9-ene: diradical conformations and stereochemical outcomes in [1,3] carbon shifts

The gas-phase thermal isomerizations at 315 °C of cis,anti,cis-tricyclo[6.4.0.0^2,7]dodec-3-ene to trans-tricyclo[6.2.2.0^2,7]dodec-9-ene and to cis,endo-tricyclo[6.2.2.0^2,7]dodec-9-ene favor the former, the more geometrically strained product, by a ratio of 2.4:1. These products correspond to suprafacial inversion (si) and suprafacial retention (sr) stereochemical outcomes. The reaction stereochemistry shown by the 11-carbon homolog, cis,anti,cis-tricyclo[6.3.0.0^2,7]undec-3-ene, is strikingly different: the [1,3] carbon shift takes place to give only the ‘forbidden’ sr product. Two related bicyclic vinylcyclobutanes, 8-deuterio- and 8-exo-methylbicyclo[4.2.0]oct-2-enes, evidence contrasting reaction stereochemical predilections in [1,3] shifts, but the 12-carbon tricyclic system and the 8-exo-methyl bicyclic analog isomerize with the same si:sr ratio! These observations prompt fresh considerations of structural influences on conformational preferences available to the alkyl, allyl diradical reactive intermediates involved.     

Total synthesis of d,1-occidentalol by photoannelation

A nine step synthesis of an intermediate previously used in the synthesis of the sesquiterpene occidentalol is reported which incorporates a 2+2 photocycloaddition reaction as the key carbon carbon bond forming step.