Birch reductions are well‐known transformations of arenes, applied for large scale synthesis of 1,4‐cyclohexadienes. Herein, we describe first reactions of benzoic acids in the presence of carbonyl compounds, affording aldol products in moderate to high yields. Alkyl aldehydes give the expected nonconjugated dienes by reaction at the α‐position. Interestingly, the intermediately formed enolate attacks aryl aldehydes and ketones from its γ‐position, which can be explained by steric hindrance. This opens the door for the one‐pot synthesis of 1,3‐cyclohexadienes, which are not accessible by classical Birch reductions. Our method is applicable to benzoic, m‐ and p‐toluic acid and various carbonyl compounds, and more than 25 new products were isolated in up to 93% yield. Prochiral aryl aldehydes afford diastereomeric mixtures in ratios of about 4:1, but in the cyclohexadiene ring only trans isomers are formed with high selectivity. Finally, the 1,3‐cyclohexadienes are suitable precursors for further transformations, which we have demonstrated in first examples. Thus, aromatization affords products of a formal meta selective Friedel‐Crafts alkylation, and four new stereocenters were generated by cycloaddition of singlet oxygen with excellent selectivity.

中文翻译：

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羰基化合物存在下 Birch 还原一锅法合成 1,3-环己二烯

Birch 还原是众所周知的芳烃转化，应用于 1,4-环己二烯的大规模合成。在此，我们描述了苯甲酸在羰基化合物存在下的首次反应，以中等到高产率提供羟醛产物。烷基醛通过 α 位反应得到预期的非共轭二烯。有趣的是，中间形成的烯醇化物从其γ位攻击芳基醛和酮，这可以通过空间位阻来解释。这为 1,3-环己二烯的一锅合成打开了大门，这是经典 Birch 还原无法实现的。我们的方法适用于苯甲酸、间甲苯甲酸和对甲苯甲酸以及各种羰基化合物，并分离出超过 25 种新产品，收率高达 93%。前手性芳基醛以约4:1的比例提供非对映异构体混合物，但在环己二烯环中仅以高选择性形成反式异构体。最后，1,3-环己二烯是适合进一步转化的前体，我们在第一个例子中已经证明了这一点。因此，芳构化提供了正式的间位选择性弗里德尔-克来福特烷基化产物，并且通过单线态氧的环加成以优异的选择性生成了四个新的立体中心。