Functional groups incompatibility

The same authors also published a simple one-pot protocol for the azide to carbamate transformation using a variety of chloroformates.21 This preparation is excellent for azide to carbamate transformations (such as Cbz, Troc, and Alloc) that would clearly not be feasible via the one-pot catalytic hydrogenation/protection preparations due to functional group incompatibility. Trimethylphosphine is the phosphine of choice once again. As the rapid and room temperature conversion of 33 to intermediate 34 illustrates, the use of trimethylphosphine allows for excellent yields under mild conditions. 

Ultimately, after many years we have come to the conclusion that introduction of the sulfinylnorvaline moiety at a late stage is fraught with functional group incompatibilities, and that in order to synthesize ustiloxin A we most likely need to constmct a dopa-sulfinylnorvaline adduct similar to 74, then incorporate our AAA-Ugi method employed for ustiloxin D with the sulfinyl-norvaline side chain aheady installed. Will we ever embark on this It depends if 1 can wait long enough for the ustiloxin project to fade from the students corporate memory yet again, and have the right student arrive at my door. 

While olehns, free carboxylic acids, amines, amides, unprotected alcohols and azides are not tolerated, esters and epoxides are, even though the reaction conditions might appear to render these functional groups incompatible. The reaction is only feasible for tertiary or benzylic C—H bonds secondary C—H bonds are not productively functionalized. 

The conversion of alcohols into ynol ethers has been achieved [188, 189]. This methodology requires the use of powerful bases thus, the potential for functional group incompatibility needs to be addressed prior to implementation of this approach Ynol ethers have been generated from gem-dibromoalkenes through initial formation of a brominated vinyl ether followed by elimination [193] Terminal aUcynes are convenient starting points for this chemistry and several excellent approaches are known [187, 191, 192]... 

However, despite some remarkable advances, only few of the known methods are capable of offering an economic and practical oxidation toward a particular industrially important transformation. Many of the found catalytic systems suffer from high reagent cost, instability, employment of hazardous metals or oxidants, harsh reaction conditions, operational complexity, functional group incompatibility, or production of unprocessable wastes.Thus, there is a continuing demand for new catalytic systems that could overcome such challenges. 

Both methods are reported to produce the a-alkyl ketones from the hydrazones without epimerization. In addition to the inherent functional group incompatibility, a notable limitation of each of these methods is that the auxiliary is liberated in an altered form, which significantly limits, or in some cases prohibits, recycling of the auxiliaries. 

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