Functionalized acetates

Several monoalkylations of functionalized acetates (Eq. 35) have been described in a series of papers the reactions were performed on potassium carbonate, either pure or mixed with potassium hydroxide. Some significant results are given in Tab. 5.13. 

Although some specific functional groups in these molecules are incompatible with the current method, the fact that 3-formylrifamycin is bound and cleaved in excellent yield demonstrates that several sensitive functionalities (acetal, enol ether, ketone, dienoate) are well tolerated. Various positions of the antibiotic could be acylated selectively. 

The hthiation of the to-chloro acetal 230 using a catalytic amount of naphthalene (4%) in THF at —78°C gave the corresponding masked tu-lithio enolate 231, which reacted with different electrophiles at —78 °C to room temperature yielding, after hydrolysis with water, the expected functionalized acetals 232 (Scheme 78) . 

C. Fayet and J. Gelas, Reaction of mono- and oligo-saccharides with keto or ethylenic enol ethers as a route to functionalized acetals and monomers for polymerization, Carbohydr. Res. 259 177 (1993). 

Recently, comprehensive World Wide Web (Internet) databases have been established on insect pheromones and semiochemicals The Pherolist , a database of chemicals identified from sex pheromone glands of female lepidopteran insects and other chemicals attractive to male moths (Am et al., 1999) and The Pherobase , a database of pheromones and semiochemicals for Lepidoptera and other insect orders (El-Sayed, 2006). These large databases on behavior modifying chemicals have extensive cross-linkages for animal taxa, indexes of compounds and source (reference) indexes. The indexes include those compounds cited in this chapter and many more with pheromone and semiochemical function acetate esters, diols, epoxides, ethers, ketones and secondary alcohols. For example, The Pherolist reports approximately 90 epoxy derivatives of C17-C23 of n-alkancs, mono-alkenes and di-alkenes as insect semiochemicals. 

Once the retrosynthetic analysis is done, we can go back and use our knowledge of chemistry to think of reagents corresponding to these synthons. Here, for example, we should certainly choose the anion of the phenol as the nucleophile and some functionalized acetic acid molecule with a leaving group in the a position,... 

Acetals, ketals, and their parent carbonyl compounds participate in this reaction [51]. Both simple and functionalized acetals undergo this reaction, as shown in Eq. (55) [173]. Double allylation was noted for the spiro-acetals with 2 equiv. allylsi-lane in the presence of TiCU (Eq. 56) [174,175]. Poly-acetals with the structure shown in Eq. (57) underwent clean production of a single product [176],... 

Addition of secondary alcohol 112 to 1-methoxyallene (113) occurred selectively at the C-1 position as expected to form the acetal 114 using Pd(OAc)2 and DPPP [34]. The reaction of the alcohol 115 with benzyloxyallene was applied to the synthesis of highly functionalized acetal 116 [35]. 

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