Novel Organic Syntheses by Reconstruction of Carbon Skeletons via Catalytic Carbon-Carbon Bond Cleavage

C-C键的催化断裂一直是有机化学和金属有机化学领域中最困难的挑战之一。这种化学最近受到了科学和技术的极大关注，并为合成有机化学的新领域打开了大门。下一个具有挑战性的课题是在C-C键断裂后重建新的碳骨架，从而导致快速和选择性地合成新的有机分子，这是传统合成方法的简单组合所不能获得的。在我们最近的研究报道中，首次对高烯丙基叔醇的β-碳消除选择性脱烯丙基反应机理进行了理论研究。然后，我们重点研究了适合于C-C键断裂的环丙烯酮和环丁烯酮的反应活性。经过多次实验，我们开发了一种前所未有的环丙烯酮的C-C键断裂羰基化二聚反应，高产率地合成了一种新型的有机功能单体吡喃并二酮。此外，还发现环丙烯酮与炔的交叉羰基化反应可得到不对称取代的吡喃并吡喃二酮。另一方面，也开发了新颖的环丁烯酮二聚为2-吡喃酮的季铵盐催化剂。该反应可以通过η4-乙烯基烯酮中间体进行。该反应也被一些铑络合物催化，然而，在使用钌（富Z）和铑（富E）催化剂的反应之间，外部烯基取代基的立体化学完全不同。

The catalytic cleavage of C-C bonds has been one of the most difficult challenges in the fields of organic and organometallic chemistry. This chemistry has recently received much scientific and technological interest, and has opened the door to a new field of synthetic organic chemistry. The next challenging subject is the reconstruction of new carbon skeletons after C-C bond cleavag, leading to the rapid and selective synthesis of novel organic molecules which can not be obtained by the simple combination of traditional synthetic methods. Among our recent reports on the ruthenium-catalyzed C-C bond cleaving reactions, the theoretical study for mechanism on the selective deallylation of tertiary homoallyl alcohols involving β-carbon elimi nation was first carried out. Then, we focused our attention on the reactivity of cyclopropenones and cyclobutenones which are the suitable strained organic molecules for C-C bond cleavage. After many trials, we developed an unprecedented ruthenium-catalvzed carbonylative dimerization of cyclopropenones involving C-C bond cleavage, which gave a novel organic functional monomer, pyranopyrandiones, in high yield. Furthermore, cross-carbonylation of cycloprorenones with alkynes was also found to give unsymmetrically substituted pyranopyrandiones. On the other hand, novel ruthenium-catalyzed dimerization of cyclobutenones to 2-pyranones has also been developed. This reaction may proceed via an η4-vinylketene intermediate, The reaction was also catalyzed by some rhodium complexes, however, the stereochemistry of the external alkenyl-substituent is totally different between the reactions using ruthenium (Z rich) and rhodium (E rich) catalysts.