Pedro de Armas

Asymmetric Alkynylation of Imines by Cooperative Hydrogen Bonding and Metal Catalysis

We thank the Spanish MCINN (CTQ2008‐06806‐C02‐02), MSC ISCIII (RETICS RD06/0020/1046) and FUNCIS (REDESFAC PI 01/06 and 35/06) for financial support.

Intramolecular hydrogen abstraction. Hypervalent organoiodine compounds, convenient reagents for alkoxyl radical generation

The photolyses of 5α-cholestane-3β,6β-diol 3-acetate (1), 5α-cholestan-2β-ol (4), 5α-cholestan-4β-ol (8), (20R)-pregn-5-ene-3β,20-diol 3-acetate (19), (20S)-pregn-5-ene-3β,20-diol 3-acetate (21), and dihydrotigogenin 3-acetate (25) in the presence of iodine and various hypervalent organoiodine compounds lead to alkoxyl radicals which undergo intramolecular hydrogen abstraction to produce, in most cases, 1,4-iodohydrins and tetrahydrofuran derivatives.

Steroidal N-nitroamines. Part 4. Intramolecular functionalization of N-nitroamine radicals: synthesis of 1,4-nitroimine compounds

Photolysis of 6β-nitroamino-5α-cholestane (4), 6β-nitroamino-5α-cholestan-3β-yl-acetate (5), 2β-nitroamino-5α-cholestane (13), 4β-nitroamino-5α-cholestane (17), (20R)-20-nitroaminopregn-5-en-3β-yl acetate (26), (20R)-(31) and (20S)-(34)-nitroamino-5α-pregnan-3β-yl acetate, (23R, 25S)-3β-acetoxy-23-nitroamino-5β-spirostan (46), 3β-nitroaminofriedelane (53), and methyl 3β-nitroaminofriedelan-29-oate (54) in the presence of iodine and various oxidative reagents leads to neutral nitroaminyl radicals which undergo intramolecular hydrogen-abstraction to produce in most cases N-nitroimine compounds. Best results were obtained with the system iodine and (diacetoxyiodo) benzene.

Water-compatible hydrogen-bond activation: A scalable and organocatalytic model for the stereoselective multicomponent aza-henry reaction

We thank the Spanish MICINN (FEDER) for financial support (CTQ2011-28417-C02-02) and CSIC for a JAE-PRE grant (F. C.-A.).

Diastereoselective formal synthesis of the antifungal agent, (+)-Preussin. A new entry to chiral pyrrolidines

Abstract A formal total synthesis of (+)-Preussin was achieved by using D-mannose as the starting material. The key step involved diastereoselective addition of allyltrimethylsilane to the bicyclic ketal 5.

Sodium borohydride-amberlyst-15 (H+): An effective reductor for hindered and unreactive ketones in aprotic solvent

Abstract The combination of sodium borohydride and amberlyst-15(H + ) in tetrahydrofurane is a powerful reductor for unreactive ketones. The reduction is fast, high-yielding and the work-up is extremely simple. Ketals, silyl ethers and other organic functions are not disturbed during the reduction.

Fragmentation of carbohydrate anomeric alkoxy radicals. A new general synthesis of cyclic ketoses

Abstract Cyclic ketones can be specifically obtained when C2 hydroxymethylated carbohydrates undergo a tandem β-fragmentation-cyclization reaction promoted by the system iodosylbenzene-iodine, under mild conditions. Pentuloses and hexuloses in furanose and pyranose form are obtained via 1,5 and 1,6 intramolecular cyclization.

Enantioselective Synthesis of Medium-Sized Ring-Bridged Oxabicycles by Ring-Closing Metathesis

We gratefully acknowledge financial support by the Spanish Ministerio de Ciencia y Tecnologia (PB98-0443-C02-02), the Canary Islands Consejeria de Educacion y Ciencia (COFI2000/03), and the FEDER (ISD97-0747-C4-01)

Stereoselective Radical C-C Bond Forming using Suarez' Protocol: A Non Reductive Process.

Abstract Suarez β-fragmentation of carbohydrate lactols induces C-C bond forming, by a non reductive process This tandem β-fragmentation-cyclization reaction of carbohydrate lactol derivatives 1,2,5 produces stereoselective carbocycles 2,4,6 in moderate yield.

Reduction of aliphatic nitramines. Approach to the synthesis of nitrosamines and amines

Abstract Deoxygenation of several aliphatic nitramines with tributyltin hydride in the presence of AIBN led to the formation of the corresponding nitrosamines. The nitrosamines underwent denitrosation when submitted to further treatment with tributyltin hydride. The 19-methyl steroid (9) was synthesized by α-alkylation of the nitrosamine (2).