Tandem Ene Research Articles

Tandem Ene/[4 + 2] Cycloaddition Reaction for the Synthesis of 9-Benzylphenanthrenes from Arynes and α-(Bromomethyl)styrenes.

A tandem reaction for the synthesis of phenanthrenes from arynes and α-(bromomethyl)styrenes is reported. The transformation proceeds via an ene reaction of α-(bromomethyl)styrenes with arynes, followed by a [4 + 2] cycloaddition reaction. The reaction generates 9-benzylphenanthrene derivatives in moderate to excellent yields.

Reaction of Carboryne with Alkylbenzenes

Carboryne (1,2-dehydro-o-carborane), in situ generated from the precursor 1-iodo-2-lithiocarborane, reacted with alkylbenzenes to give two regioisomers of the [4 + 2] cycloadducts as the major products in moderate to good yields, in which the steric factors play an important role in the regioselectivity. Minor products derived from benzylic C–H insertion reaction, annulation reaction, tandem [4 + 2] cycloaddition/homo Diels–Alder reaction, and tandem ene reaction/[2 + 2] cycloaddition were also isolated and characterized in the reaction of carboryne with toluene. The presence of AgF in the above reaction produced no notable changes in the product distributions and yields.

ChemInform Abstract: Towards a Biomimetic Synthesis of the Marine Alkaloids Papuamine and Haliclonadiamine: Model Studies.

Abstract A plausible biosynthetic pathway for the isomeric marine alkaloids papuamine and haliclonadiamine via the double tandem ene cyclisation of a tetraenediimine is proposed. Initial model studies directed toward the biomimetic synthesis of these alkaloids are described which illustrate that the Lewis acid-promoted ene cyclisation of methyl-2-(methoxycarbonyl)dodeca-2,8-dienoate is critically dependent on the Δ-8 geometry.

ChemInform Abstract: Total Synthesis of ent‐Lepadin F (IIIa) and G (IIIb) by a Tandem Ene—Yne—Ene Ring Closing Metathesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Total Synthesis of ent-Lepadin F and G by a Tandem Ene−Yne−Ene Ring Closing Metathesis

The first total synthesis of the decahydroquinoline-alkaloids lepadin F and G is described. As key steps, the decahydroquinoline skeleton has been synthesized by utilizing a tandem ene-yne-ene ring closing metathesis of an acyclic precursor followed by a stereoselective hydrogenation of the resulting diene moiety. The selectivity of these two steps was achieved by a well-directed hydroxyl protection strategy. The synthesized compounds were found to be enantiomers of natural lepadin F and G, consequently the absolute configuration of the natural compounds could be assigned.

Total Syntheses of Four Stereoisomers of 4α-Hydroxy-1β,7β-peroxy- 10βH-guaia-5-ene

[reaction: see text]. The first total syntheses of four stereoisomers of 4alpha-hydroxy-1beta,7beta-peroxy-10betaH-guaia-5-ene are reported starting from the readily available (+)-dihydrocarvone. These compounds have been synthesized from dienes (-)-isoguaiene and (-)-10-epi-isoguaiene by tandem ene hydroperoxylation-[4 + 2] cycloaddition with O(2) followed by selective reduction. The structure of the natural 4alpha-hydroxy-1beta,7beta-peroxy-10betaH-guaia-5-ene isolated from Liabum floribundum has been confirmed.

Connective Synthesis of Polysubstituted Tetrahydropyrans by a Novel and Stereocontrolled Metallo‐ene/Intramolecular Sakurai Cyclization Sequence.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Connective synthesis of polysubstituted tetrahydropyrans by a novel and stereocontrolled metallo-ene/Intramolecular Sakurai Cyclization sequence.

A novel methodology based upon the allylmetalation step followed by an Intramolecular Sakurai Cyclization (IMSC) provides an efficient access to a variety of tetrahydropyran derivatives. This new strategy nicely complements our initial protocol that embodied a tandem ene reaction/IMSC sequence. Both mono- and dihydroxy-tetrahydropyrans could be easily assembled with complete stereocontrol at the various chiral centers.

ChemInform Abstract: Tandem Ene Addition/Diels-Alder Cycloaddition Reactions of Methyl Linoleate with 4-Phenyl-1,2,4-triazoline-3,5-dione and Diethyl Azodicarboxylate.

Treatment of methyl linoleate with 4-phenyl-1,2,4-triazoline-3,5-dione affords 1:1 adducts resulting from ene addition, and 1:2 adducts formed by ene addition followed by Diels Alder cycloaddition....

Tandem Ene Addition/Diels-Alder Cycloaddition reactions of Methyl Linoleate with 4-Phenyl-1,2,4-Triazoline-3,5-Dione and Diethyl Azodicarboxylate

Treatment of methyl linoleate with 4-phenyl-1,2,4-triazoline-3,5-dione affords 1:1 adducts resulting from ene addition, and 1:2 adducts formed by ene addition followed by Diels Alder cycloaddition. The corresponding reaction of diethyl azodicarboxylate yields predominantly 1:1 ene products.

Towards a Biomimetic Synthesis of the Marine Alkaloids Papuamine and Haliclonadiamine: Model Studies

A plausible biosynthetic pathway for the isomeric marine alkaloids papuamine and haliclonadiamine via the double tandem ene cyclisation of a tetraenediimine is proposed. Initial model studies directed toward the biomimetic synthesis of these alkaloids are described which illustrate that the Lewis acid-promoted ene cyclisation of methyl-2-(methoxycarbonyl)dodeca-2,8-dienoate is critically dependent on the Δ-8 geometry.

Organophosphorus Compounds, 121. Phosphaalkynes in Ene Reactions with Alkylidenecyclopropanes and Allenes

AbstractPhosphaalkynes readily participate in ene reactions both with alkylidenecyclopropanes and with allenes to furnish phosphaalkenes (the products of a simple ene reaction) and phosphanes (the products of a tandem ene reaction). Thus, irrespective of the stoichiometry, the thermal reactions of the phosphaalkynes 1a‐c with isopropylidenecyclopropane (8) or cyclopropylidenecyclopentane (11) proceed by a tandem ene process with retention of the three‐membered ring unit to furnish the corresponding bis(cyclopropyl)phosphanes 10a‐c or 12. In contrast, with cyclopropylidenecyclohexane (13) as the H‐donor, the specific formation of either the monoadducts 14a,c or of the bisadducts 15a,c can be controlled. A crystal structure analysis of 15a confirmed the structures of the tandem ene products while the constitutions and configurations of the novel P‐cyclopropylphosphaalkenes 14a,c were unequivocally elucidated by an X‐ray crystal structure analysis of the corresponding, W(CO)5‐complexed system 16. Alkylated allenes such as 1,1‐dimethylallene (17), vinylidenecyclohexane (20), tetramethylallene (22), or 1,2‐cyclononadiene (24) undergo thermal addition by way of a double ene process to afford the phosphaalkynes 1. In each case, regiospecific attack of the phosphorus atom at the central C‐atom of the cumulene system results in the formation of the structurally unique phosphanes 21, 23a,b, and 25a,b. On the other hand, thermal reactions of 1a,b in the presence of 1,1‐diethylallene (26) come to a standstill after the first ene addition and furnish the cross‐conjugated phosphatrienes 27a,b as the first representatives of the previously unknown phospha[3]dendralene system. The thermally initiated tandem ene reactions of the phosphaalkynes 1 with propadiene (28) or tert‐butylallene (30) each proceed through transfer of a vinylic hydrogen atom from the ene to the enophile to afford the bis(propargyl)phosphanes 29a,b and 31, respectively, as addition products.

Step growth polymerization via tandem ene and diels‐alder reactions

AbstractIn contrast to other electron deficient enophiles or dienophiles which react with 1,4‐cyclohexadiene (1,4‐CHD) under aromatization, 1,2,4‐triazoline‐3,5‐diones react in a defined reaction sequence. In a first step the 1,4‐cyclohexadiene reacts via an ene‐reaction. The intermediately formed substituted 1,3‐cyclohexadiene immediately reacts in a Diels‐Alder reaction. The regiochemistry of the Diels‐Alder reaction is controlled by the solvent polarity. This reaction sequence can be used to synthesize polymers. Low‐molarmass model compounds were synthesized to elucidate the stereochemistry of the polymers. By varying the bistriazolinedione, polymers with backbones of different rigidity are available.

ChemInform Abstract: Organophosphorus Compounds. Part 106. Tandem Ene Reactions of Phosphaalkynes with Terminal Alkenes as All‐Carbon Enes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Organophosphorus Compounds; 106. Tandem Ene Reactions of Phosphaalkynes with Terminal Alkenes as All-Carbon Enes

Organophosphorus Compounds; 106. Tandem Ene Reactions of Phosphaalkynes with Terminal Alkenes as All-Carbon Enes

Intramolecular ene reactions, III. Diastereoselective formation of cyclohexanes by intramolecular ene reactions of 1,7‐dienes

AbstractThe 1,7‐dienes 3a–c with a double‐activated enophile moiety undergo thermal and zinc bromide catalyzed intramolecular ene reactions leading to trans‐1,2‐disubstituted cyclohexanes 4a – c in up to 89% yield, highly diastereoselectively. The synthesis of cyclohexanes from 1,7‐dienes has not been feasible so far in a selective way and with good yields. Reaction of 3d, 3e, and 3f gives mixtures of intramolecular hetero Diels‐Alder adducts, ene and tandem ene products. The 1,7‐dienes 3 are obtained by Knoevenagel condensation of 7‐methyl‐6‐octenal (2) with acyclic 1,3‐dicarbonyl and analogous compounds 1.