Intramolecular Dehydro Diels Research Articles

A Removable Acyl Group Promoted the Intramolecular Dehydro-Diels-Alder Reaction of Styrene-Ynes: Highly Chemoselective Synthesis of Aryldihydronaphthalene Derivatives.

A removable acyl group promoted the intramolecular didehydro-Diels-Alder reaction of styrene-ynes under mild reaction conditions is proposed. The reaction is free of metals and catalysts, is easy to perform, and exhibits good functional group tolerance, providing a highly chemoselective approach for obtaining the valuable aryldihydronaphthalene derivatives.

Heat Versus Basic Conditions: Intramolecular Dehydro-Diels–Alder Reaction of 1-Indolyl-1,6-heptadiynes for the Selective Synthesis of Substituted Carbazoles

The intramolecular dehydro-Diels–Alder reaction of 1-indolyl-1,6-heptadiynes proceeds smoothly under rather mild heating conditions to give substituted carbazoles in moderate to good yields. The reaction of 7-aryl-1-indolyl-1,6-heptadiynes under heating gives the corresponding carbazoles chemoselectively in high yields, whereas the reaction under basic conditions gives naphthalenes as major products.

Intramolecular dehydro-Diels-Alder reaction affords selective entry to arylnaphthalene or aryldihydronaphthalene lignans.

Intramolecular dehydro-Diels–Alder (DDA) reactions are performed affording arylnaphthalene or aryldihydronaphthalene lactones selectively as determined by choice of reaction solvent. This constitutes the first report of an entirely selective formation of arylnaphthalene lactones utilizing DDA reactions of styrene-ynes. The synthetic utility of the DDA reaction is demonstrated by the synthesis of taiwanin C, retrohelioxanthin, justicidin B, isojusticidin B, and their dihydronaphthalene derivatives. Computational methods for chemical shift assignment are presented that allow for regioisomeric lignans to be distinguished.

Synthesis of carbazoles by dehydro Diels–Alder reactions of ynamides

A new approach to carbazoles and benzannulated carbazoles by means of intramolecular dehydro Diels–Alder of ynamides is reported. N-( o-Ethynyl)aryl ynamides and N-( o-ethynyl) arylynamides were prepared in a few steps starting from o-iodoaniline. Thermal cycloaddition of N-( o-ethynyl)aryl ynamides and N-( o-ethynyl) arylynamides affords carbazoles and benzannulated and heteroannulated carbazoles in moderate-to-good yields.

Synthesis of Carbazoles from Ynamides by Intramolecular Dehydro Diels—Alder Reactions.

A new approach to carbazoles and benzannulated carbazoles by means of intramolecular dehydro Diels−Alder reactions of ynamides is reported. By using this approach, carbazoles and benzo[b]-, tetrahydrobenzo[b]-, naphtho[1,2-b]-, naphtho[2,1-b]-, and dibenzo[a,c]carbazoles have been prepared in moderate-to-good yields.

Density functional study on intramolecular dehydro Diels–Alder reactions of conjugated enynes

The effects of several substituents X on the intramolecular dehydro Diels–Alder reactions of conjugated enynes ( 1R– 9R) were investigated at the B3LYP/6-311G(d,p) level of theory. Geometry optimizations and harmonic frequency calculations were performed for all reactants, transition structures, as well as products. It has shown that all transition structures are asynchronous, with forming C 4C 8 bond length being shorter than C 1C 9 distance except for 9TS. 7R with the protonated amino ( X = NH 2 + ) function displays a lower barrier than 6R with the amino (X=NH) function. The intramolecular [4+2] cycloaddition with X=O has the lowest reaction barrier and the highest exothermicity.

Synthesis of Carbazoles from Ynamides by Intramolecular Dehydro Diels−Alder Reactions

[reaction: see text]. A new approach to carbazoles and benzannulated carbazoles by means of intramolecular dehydro Diels-Alder reactions of ynamides is reported. By using this approach, carbazoles and benzo[b]-, tetrahydrobenzo[b]-, naphtho[1,2-b]-, naphtho[2,1-b]-, and dibenzo[a,c]carbazoles have been prepared in moderate-to-good yields.

Intramolecular Dehydro Diels—Alder Reactions of Diarylacetylenes: Switching Between Benzo[b]‐ and Benzo[c]fluorenones as Products by Controlling the Rearrangement of Cyclic Allene Intermediates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Intramolecular dehydro Diels-Alder reactions of diarylacetylenes: switching between benzo[b]- and benzo[c]fluorenones as products by controlling the rearrangement of cyclic allene intermediates.

Thermal cyclization of 1-[2-(arylethynyl)phenyl]-3-trimethylsilylpropynones affords a mixture of benzo[b]fluorenones and benzo[c]fluorenones. The ratio of the two isomers can be efficiently varied between 100:0 and 0:100 by introducing substituents with appropriate electronic and steric properties on the aryl rings and using an appropriate solvent.

Synthesis of the Tetracyclic Core of Anthracycline Antibiotics by an Intramolecular Dehydro Diels—Alder Approach.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of the tetracyclic core of anthracycline antibiotics by an intramolecular dehydro Diels-Alder approach.

[reaction: see text] A conceptually new approach to the tetracyclic core of the anthracycline antibiotics is reported. With use of this approach, the 7,8,9,10-tetrahydronaphthacene-5,12-dione skeleton has been synthesized in three steps, from commercially available reagents, in yields of up to 85%.

A new rearrangement of cyclic allenes via 1,2-dehydro[10]annulenes: formation of benzo[ c]fluorenones

A new rearrangement of cyclic allenes giving benzo[ c]fluorenones was observed when studying intramolecular dehydro Diels–Alder reactions of silyl-substituted alkynes with arenynes (aryldiacetylenes).