Synthetic Execution

The strategic design a detailed retrosynthetic analysis The synthetic execution methodologies, reagents, and conditions to be used... 

The tactical use of this rearrangement is important in the context of the broader strategic plan. The combination of the electron-deficient diene (201) and the electron-rich dienophile (202) sets up a cycloaddition reaction that proceeds at a convenient rate and with desired regiocontrol. The recognition that, after the rearrangement, the sulfoxide is the synthetic equivalent of an allylic alcohol exemplifies brilliant strategic planning and synthetic execution. 

Retrosynthetic. The direction of chemical change opposite to that of laboratory execution of a reaction (synthetic direction) the reverse-synthetic sense. 

The parent TMM precursor (1), now commercially available, has played a pivotal role in the execution of many synthetic plans directed at natural and unnatural targets. Reaction of (1) with 2-(methoxycarbonyl)cyclohexenone (14, R=C02Me) in the presence of palladium acetate and triethyl phosphite produced the adduct (15) in near quantitative yield. This cycloadduct is a critical intermediate in the total synthesis of a hydroxykempenone (16), a component of the defensive substances secreted by termites (Scheme 2.5) [12]. In accord with a previous observation by Trost that unactivated 2-cyclohexenone reacts poorly with TMM-Pd [13], the substrate (14, R=Me) was essentially inert in the cycloaddition. 

Three operations usually accompany the carrying out of a reaction on a synthetic scale stirring, addition of a reagent, and temperature control. Most often, a threenecked round-bottom flask allows simultaneous execution of these operations along with certain other controls that may be desirable, such as introduction of an inert atmosphere or maintenance of reflux. In what follows, a short description of a suitable method of carrying out each of the operations is given. 

This volume of Organic Syntheses contains twenty-seven checked procedures of value to the modern practicing chemist. One hopes it will also serve to attract students to the charms of skillfully planned and executed experimental work. The majority of the preparations represent specific examples of important, often recently discovered synthetic methods with general applicability. As in previous volumes the preparation of a number of reagents and widely used starting materials is also included. 

Szczepaikiewicz et al. [85] reported the synthesis of pyrazoles (e.g., 167) from the diketone 168 with hydrazine hydrate, shown in Scheme 43. Nigram et al. executed a similar synthetic sequence [86]. 

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