ABSTRACT
Carbinol-tethered octalin-diols (1), which differ only by the C11 configuration at the angular position, were transformed selectively to three types of structurally unrelated original scaffolds such as unsymmetrical octahydroanthracenes (5/7), furofuranes (6), or spirans (8/9) via a two-step protocol. The 11S* configuration ensures a C13-C4 Friedel-Crafts type C-C bonding (through an unprecedented oxidative cleavage-triggered domino process) while the 11R* configuration allows for a C13-C2 Marson-type Friedel-Crafts C-C bonding (through a nucleophilic acetal opening).
Subject(s)
Acetals/chemical synthesis , Alcohols/chemical synthesis , Polycyclic Aromatic Hydrocarbons/chemical synthesis , Acetals/chemistry , Alcohols/chemistry , Catalysis , Molecular Structure , Oxidation-Reduction , Polycyclic Aromatic Hydrocarbons/chemistry , StereoisomerismABSTRACT
Structurally different products can be reached selectively from unsaturated vicinal bicyclic diols, which differ only by the epoxide configuration at the angular position. It is possible to modify the regiochemical outcome of the domino process in such a way as to create a different pathway, [4 + 2] versus [4 + 3 + 2], and control product distribution by using the configuration bias. No previous example of a domino variant of the [4 + 3 + 2] process appears to have been documented.
Subject(s)
Combinatorial Chemistry Techniques , Epoxy Compounds/chemistry , Models, Molecular , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Molecular Structure , StereoisomerismABSTRACT
Bicyclic unsaturated diols undergo a path selective modular domino transformation upon subjection to Pb(OAc)4, the reaction being biased to the nature of the angular substituent. The magnitude of the linking chain and the nature of the angular substituent determine the reaction course. Methylene ether linkage acts as an autoremovable directing group (ring-retained domino product 5), whereas a propylene linkage switches the path toward the ring-expanded type 21 domino product. Reaction times were substantially reduced using microwave irradiation.
Subject(s)
Alkenes/chemistry , Ether/chemistry , Microwaves , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Organometallic Compounds/chemistry , Time FactorsABSTRACT
The octaline diol system 6 was found to undergo an interesting set of reactions upon treatment with PhI(OAc)2, leading, in a single synthetic operation, to complex oxygen heterocycles. Experimental evidence supports an intramolecular hetero[4 + 2 + 2] adduct that has heretofore never been observed, which completely dominates the hetero[4 + 2] path in several cases. The domino protocol can be biased one way or another depending on both the nature of the pi-system and the length of the methylene spacer at the angular position.
Subject(s)
Heterocyclic Compounds/chemical synthesis , Crystallography, X-Ray , Heterocyclic Compounds/chemistry , Models, Molecular , Molecular Structure , Oxidation-ReductionABSTRACT
[structure: see text]. The first enantioselective total synthesis of 1-epi-pathylactone A, 3, has been accomplished using a PhI(OAc)2-mediated domino reaction as a key step. No diastereomeric separation was required throughout the whole synthetic scheme presented in this paper. Comparison of 1H and 13C NMR spectral data of the synthetic product with the reported spectral data of natural pathylactone A, coupled with an X-ray crystallographic analysis, led to the conclusion that the C1 configuration in the original paper was erroneously ascribed to (R).
Subject(s)
Bridged-Ring Compounds/chemical synthesis , Lactones/chemical synthesis , Sesquiterpenes/chemical synthesis , Spiro Compounds/chemical synthesis , Bridged-Ring Compounds/chemistry , Crystallography, X-Ray , Lactones/chemistry , Models, Molecular , Molecular Structure , Sesquiterpenes/chemistry , Spiro Compounds/chemistry , StereoisomerismABSTRACT
Oxidative cleavage with lead tetraacetate results in the synthesis of different oxygen heterocycles starting from the same unsaturated 1,2-diol of type I by tuning of the substitution pattern at the angular position. When this compound bears a functional substituent, such as an alkoxy, ester, alkenyl, or simply a hydrogen, more than one reaction pathway are in competition. The process allows for the selective formation of three different complex ring systems, by the appropriate choice of the angular substituent, leading to either a ring-expanded type 1, ring-retained type 2, or domino products 3.
ABSTRACT
The microwave-assisted intramolecular [3 + 2] cycloaddition reaction of azomethine ylides to activated and nonactivated alkenes and alkynes is described. The procedure allows the synthesis of pyrrolidines and pyrrole products in good to excellent overall yields in short reaction times. It appears from parallel comparative studies that the microwave procedure favors the reaction times and overall purity of the crude reaction mixture. The reactions can also be performed in the absence of solvent. [reaction: see text]
