Direct functionalization of a variety of quinones with several boronic acids has been developed. This scalable reaction proceeds readily at room temperature in an open flask using inexpensive reagents: catalytic silver(I) nitrate in the presence of a persulfate co-oxidant. The scope with respect to quinones is broad with a variety of alkyl- and arylboronic acids undergoing efficient cross-coupling. The mechanism is presumed to proceed through a nucleophilic radical addition to the quinone with in situ reoxidation of the resulting dihydroquinone. This method has been applied to complex substrates including a steroid derivative and a farnesyl natural product.

Aliphatic primary amines are a class of chemical feedstock essential to the synthesis of higher-order nitrogen-containing molecules, commonly found in biologically active compounds and pharmaceutical agents. New methods for the construction of complex amines remain a continuous challenge to synthetic chemists. Here, we outline a general palladium-catalysed strategy for the functionalization of aliphatic C-H bonds within amino alcohols, an important class of small molecule. Central to this strategy is the temporary conversion of catalytically incompatible primary amino alcohols into hindered secondary amines that are capable of undergoing a sterically promoted palladium-catalysed C-H activation. Furthermore, a hydrogen bond between amine and catalyst intensifies interactions around the palladium and orients the aliphatic amine substituents in an ideal geometry for C-H activation. This catalytic method directly transforms simple, easily accessible amines into highly substituted, functionally concentrated and structurally diverse products, and can streamline the synthesis of biologically important amine-containing molecules.

Investigations detailed herein, including density functional theory (DFT) calculations, demonstrate that the formation of either alkoxy- or hydroxy-Ti(III) complexes considerably decreases the energy of activation for C-O bond homolysis. As a consequence of this observation, we described two new synthetic applications of Nugent's reagent in organic chemistry. The first of these applications is an one-step methodology for deoxygenation-reduction of alcohols, including benzylic and allylic alcohols and 1,2-dihydroxy compounds. Additionally, we have also proved that Ti(III) is capable of mediating carbonyl coupling-olefination. In this sense, and despite the fact that for over 35 years it has been widely accepted that either Ti(II) or Ti(0) was the active species in the reductive process of the McMurry reaction, the mechanistic evidence presented proves the involvement of Ti(III) pinacolates in the deoxygenation step of the herein described Nugent's reagent-mediated McMurry olefination. This observation sheds some light on probably one of the mechanistically more complex transformations in organic chemistry. Finally, we have also proved that both of these processes can be performed catalytically in Cp(2)TiCl(2) by using trimethylsilyl chloride (TMSCl) as the final oxygen trap.

The biosynthetic origin of most of triterpenes lies in cascade cyclizations and rearrangements of the acyclic precursors squalene (S) and 2,3-oxidosqualene (OS), processes leading to tetra- and pentacyclic triterpene skeleta. Apart from these, a number of triterpenoid structures derived from cyclization processes, that are different from those leading to tetra- and pentacyclic triterpenes, are also found in Nature. We have defined these processes as unusual cyclizations, and grouped them in three blocks, namely, incomplete cyclizations of the corresponding S-derived precursors, cyclizations of S or OS towards polycyclic triterpenes and subsequent cleavage of the preformed ring systems, and two independent cyclizations of the S- or OS-derived precursor. Apart from the molecules obtained from intact organisms, we will also consider the compounds obtained from in vitro cyclizations promoted by enzyme systems. After establishing which compounds could unambiguously be grouped under the term 'unusually cyclized triterpenes', this review moves on to the advances achieved in this kind of structure during the last ten years. These advances are presented in three parts. The first one presents the structure and biological properties of the unusual triterpenes reported in the last decade. The second part considers the main biosynthetic pathways which justify the formation of these triterpenes from their corresponding acyclic precursors. Finally, we look at the achievements made in different synthetic strategies directed at some of these molecules. One hundred and twenty-three references are cited.

As a result of a combined theoretical and experimental study, we describe a two-step protocol for the preparation of an optically pure, multifunctional, cyclopentanic core shared by a number of natural products. This process is based on a hitherto unreported Ti(III)-mediated diastereoselective cyclization in which the hydroxy-directed template effect played by the Ti(III) species was found to be crucial for the stereoselective outcome of the reaction. The viability of this concept was confirmed with the first protecting-group free synthesis of three enantiopure chokols, namely, chokols K, E, and B.

Efficient procedures based on the use of iodine for the aromatization of a series of terpenoids possessing diene and homoallylic or allylic alcohol functionalities are described. Different examples are reported as a proof-of-concept study. Furthermore, iodine also proved to mediate the dehydrogenation of testosterone.

Treatment of germacrone (1) with different electrophiles, and of its epoxy derivatives germacrone-4,5-epoxide (2), germacrone-1,10-epoxide (3) and isogermacrone-4,5-epoxide (4) with Brönsted/Lewis acids and Ti(III), gives rise to a great structural diversity. Thus, by using a maximum of two steps, the production of more than 40 compounds corresponding to 14 skeletons is described. Computational calculations rationalizing the structural divergence produced are also described. Finally, since some of the compounds generated are bioactive natural sesquiterpenes, the mechanisms of formation of these substances will provide new insights in their biosynthesis.

The first total synthesis of potent anti-inflammatory polypodanes (+)-myrrhanol A (1), (+)-myrrhanone A (2), (+)-myrrhanone B (3), and (+)-myrrhanol B (4) has been achieved. Key steps in our convergent, highly stereocontrolled route are a Ti(III)-mediated radical cyclization of a chiral monoepoxide to furnish a bicyclic synthon that combines stereospecifically with an acyclic vinyl iodide via an intermolecular B-alkyl Suzuki-Miyaura cross-coupling.