Control sequence synthesis method

Conflict Analysis in Top-down Bus Synthesis. The top-down bus synthesis method uses 2-bus models with fixed topologies. Since the fixed topologies limit the parallelism of the system, not all control sequences synthesized by the code scheduler are feasible. The inner loop of the code scheduler is a hardware conflict analysis algorithm that determines if two sets of microoperations conflict when packed into a control state. For top-down bus S5mthesis, interconnection conflicts are determined as follows ... 

According to Kravelen,( l the fundamental characteristics of a polymer are the chemical structure and the molecular mass distribution pattern. The former includes the nature of the repeating units, end groups, composition of possible branches and cross-links, and defects in the structural sequence. The molecular mass distribution, which depends upon the synthesis method, provides information about the average molecular size and its irregularities. These characteristics are responsible, directly or indirectly, forthe polymer properties. They are directly responsible forthe cohesive force, packing density and potential crystallinity, and molecular mobility (with phase transitions). Indirectly, these properties control the morphology and relaxation phenomena (behavior of the polymer). 

The general method for the preparation of diphenylpyrazolines is shown in Scheme 11.8, in which X is a suitable leaving group, usually chloro but sometimes dialkylamino. This reaction normally proceeds readily, although pH control may be important. Preparation of the substituted ketone and hydrazine intermediates needed for the synthesis may involve lengthy and complicated sequences. Further reactions are often required to modify the substitution in ring B after formation of the pyrazoline ring. The preparation of compound 11.26 shown in Scheme 11.9 illustrates one of the simpler instances. 

The transformation of the cyano group could also introduce a new chiral center under diastereoselective control (Figure 5.13). Grignard-transimination-reduction sequences have been employed in a synthesis of heterocyclic analogues of ephedrine [81]. The preferential formation of erythro-/3-amino alcohols may be explained by preferential hydride attack on the less-hindered face of the intermediate imine [82], and hydrocyanation of the imine would also appear to proceed via the same type of transition state. In the case of a,/3-unsaturated systems, reduction- transimination-reduction may be followed by protection of the /3-amino alcohol to an oxazolidinone, ozonolysis with oxidative workup, and alkali hydrolysis to give a-hydroxy-/3-amino acids [83]. This method has been successfully employed in the synthesis L-threo-sphingosine [84]. 

Complete control of the diastereoselectivity of the synthesis of 1,3-diols has been achieved by reagent selection in a one-pot tandem aldol-reduction sequence (see Scheme l). i Anti-selective method (a) employs titanium(IV) chloride at 5°C, followed by Ti(OPr )4, whereas method (b), using the tetrachloride with a base at -78 °C followed by lithium aluminium hydride, reverses the selectivity. A non-polar solvent is required (e.g. toluene or dichloromethane, not diethyl ether or THF), and at the lower temperature the titanium alkoxide cannot bring about the reduction of the aldol. Tertiary alkoxides also fail, indicating a similarity with the mechanism of Meerwein-Ponndorf reduction. 

---