The alkylation of enolates is one of the backbones of ketone chemistry, yet in practice it suffers from numerous limitations due to problems of regiochemistry (including O- versus C-alkylation), multiple alkylations, self-condensation, competing elimination, and incompatibility with many polar groups that have to be protected. Over the years, various solutions have been devised to overcome these difficulties, such as the employment of auxiliary ester or sulfone groups to modify the pK_a of the enolizable hydrogens, the passage by the corresponding hydrazones, the use of transition-metal-catalyzed redox systems to formally alkylate ketones with alcohols, etc. Most of these hurdles disappear upon switching to α-ketonyl radicals. Radicals are tolerant of most polar functions, and radical additions to flat sp² centers are generally easier to accomplish than enolate substitution at tetrahedral sp³ carbons. The main stumbling block, however, has been a lack of generally applicable methods for the generation and intermolecular capture of α-ketonyl radicals. We have found over the past years that the degenerative exchange of xanthates represents in many ways an ideal solution to this problem. It overcomes essentially all of the difficulties faced by other radical processes because of its unique ability to reversibly store reactive radicals in a dormant, nonreactive form. The lifetime of the radicals can therefore be significantly enhanced, even in the concentrated medium needed for bimolecular additions, while at the same time regulating their absolute and relative concentrations. The ability to perform intermolecular additions to highly functionalized alkene partners opens up numerous possibilities for rapid and convergent access to complex structures. Of particular importance is the elaboration of ketones that are prone to self-condensation, such trifluoroacetone, and of base-sensitive ketones, such as chloro- and dichloroacetone, since the products can be used for the synthesis of a myriad fluorinated and heteroaromatic compounds of relevance to medicinal chemistry and agrochemistry. The formal distal dialkylation of ketones, also of utmost synthetic interest, is readily accomplished, allowing convenient access to a wide array of useful ketone building blocks. Cascade processes can be implemented and, in alliance with powerful classical reactions (aldol, alkylative Birch reductions, etc.), furnish a quick route to complex polycyclic scaffolds. Furthermore, the presence of the xanthate group in the adducts can be exploited to obtain a variety of arenes and heteroarenes, such as pyrroles, thiophenes, naphthalenes, and pyridines, as well as enones, dienes, and cyclopropanes. Last but not least, the reagents and most of the starting materials are exceedingly cheap, and the reactions are safe and easy to scale up.

中文翻译：

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黄原酸酯通向酮的途径：当自由基比烯醇酸酯更好时

烯醇盐的烷基化是酮化学的主干之一，但实际上由于区域化学（包括O-与C-烷基化），多个烷基化，自缩合，竞争性消除以及与许多不相容性的问题，它受到许多限制。必须保护的极性基团。多年来，已经设计出各种解决方案来克服这些困难，例如使用辅助酯或砜基团来修饰p K _a。可烯化的氢，相应的酮通过，使用过渡金属催化的氧化还原体系将酮与醇正式烷基化等，这些障碍中的大多数在转换为α-酮基自由基时就消失了。自由基可耐受大多数极性功能，与四面体sp ³碳原子上的烯酸酯取代基相比，向平面sp ²中心自由基加成通常更容易实现。然而，主要的绊脚石是缺乏普遍适用的生成和分子间方法捕获α-酮基自由基。在过去的几年中，我们发现黄药的变性交换在许多方面代表了解决该问题的理想方法。它以其独特的能力以潜在的非反应性形式可逆地存储反应性自由基，从而基本上克服了其他自由基过程所面临的所有困难。因此，即使在双分子添加所需的浓缩培养基中，自由基的寿命也可以显着提高，同时调节其绝对和相对浓度。执行分子间的能力高度功能化的烯烃伙伴的添加为快速，收敛地访问复杂结构开辟了许多可能性。尤为重要的是精心制备易于自缩合的酮（如三氟丙酮）和对碱敏感的酮（如氯代和二氯丙酮），因为该产品可用于合成无数的氟代和杂芳族化合物。与药物化学和农业化学有关。酮的正式的远端二烷基化，也具有最大的合成意义，很容易实现，从而可以方便地获得各种有用的酮结构单元。可以实施级联过程，并与强大的经典反应（醛醇缩合，烷基化的桦木还原等）结合，为复杂的多环支架提供快速途径。此外，加合物中黄药酸酯基团的存在可用于获得各种芳烃和杂芳烃，例如吡咯，噻吩，萘和吡啶，以及烯酮，二烯和环丙烷。最后但并非最不重要的一点是，试剂和大多数起始原料都非常便宜，而且反应安全且易于扩大规模。