Successive cycloadditions domino reactions

An intermolecular 1,3-dipolar cycloaddition of diazocarbonyl compounds with alkynes was developed by using an InCl3-catalyzed cycloaddition in water. The reaction was found to proceed by a domino 1,3-dipolar cycloaddition-hydrogen (alkyl or aryl) migration (Eq. 12.68).146 The reaction is applicable to various a-diazocarbonyl compounds and alkynes with a carbonyl group at the neighboring position, and the success of the reaction was rationalized by decreasing the HOMO-LUMO of the reaction. 

The combination of pericyclic transformations as cycloadditions, sigmatropic rearrangements, electrocydic reactions and ene reactions with each other, and also with non-pericyclic transformations, allows a very rapid increase in the complexity of products. As most of the pericyclic reactions run quite well under neutral or mild Lewis acid acidic conditions, many different set-ups are possible. The majority of the published pericyclic domino reactions deals with two successive cycloadditions, mostly as [4+2]/[4+2] combinations, but there are also [2+2], [2+5], [4+3] (Nazarov), [5+2], and [6+2] cycloadditions. Although there are many examples of the combination of hetero-Diels-Alder reactions with 1,3-dipolar cycloadditions (see Section 4.1), no examples could be found of a domino all-carbon-[4+2]/[3+2] cycloaddition. Co-catalyzed [2+2+2] cycloadditions will be discussed in Chapter 6. 

Apart from Baran s approach using a naturally abundant starting material with a partially assembled carbon skeleton, the group of Sorensen [146] opted for a fuUy synthetic access to the tetracyclic core stracture of the cortistatin family. Their route relied on a domino cyclodearomatization/l,3-dipolar cycloaddition reaction that successively formed the highly oxygenated A and B rings in one process (Scheme 14.56). 

AMI, B3LYP/6-31G //AMl, and B3LYP/6-31G computational studies have been used to investigate the molecular mechanism of the domino cycloadditions between DMAD and naphthalino- and anthraceno-furanophanes. The transannular Diels-Alder reaction of the furanophane (143) successfully produced the desired isomer (144), a key intermediate in the total synthesis of the diterpenoid chatancin (Scheme 55). ... 

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