117471-21-3

Upstream product

• 873-66-5 1-propenylbenzene 
• 2880-58-2 2-methoxy-1,4-benzoquinone 
• 637-50-3 1-phenylpropene 
• 766-90-5 cis-1-phenyl-1-propylene 
• 90-05-1 2-methoxy-phenol 

Downstream Products

• 21008-39-9 (2R,3S)-6-Methoxy-3-methyl-2-phenyl-2,3-dihydro-benzofuran-5-ol 
• 21008-39-9 (+/-)-Obtusafuran 

Relevant academic research and scientific papers

Asymmetric reactions of 2-methoxy-1,4-benzoquinones with styrenyl systems: Enantioselective syntheses of 8-aryl-3-methoxybicyclo[4.2.0]oct-3- en-2,5-diones, 7-Aryl-3-hydroxybicyclo[3.2.1]oct-3-en-2,8-diones, 2-Aryl-6- methoxy-2,3-dihydrobenzofuran-5-ols, and pterocarpans

Reactions of 2-methoxy-1,4-benzoquinones 2 and 3 with (E)- propenylbenzenes 1 promoted at -78 °C by Ti(IV)-TADDOLates prepared from diol-(+)-4 afford (1R,6R,7R,8R)-8-aryl-3-methoxy-7-methylbicyclo[4.2.0]oct- 3-en-2,5-diones 5/8 or (1R,5R,6R,7R)-7-aryl-3-hydroxy-6-methylbicyclo[3.2.1]- oct-3-en-2,8-diones 7/10 in good yield and high ee. (2S,3S)-2-Aryl-6-methoxy- 3-methyl-2,3-dihydrobenzofuran-5-ols 6/9 are also found, but in slightly lower ee. Cyclobutanes 5/8 cleanly and efficiently rearrange to the dihydrobenzofurans 6/9 without loss of enantiomeric purity upon treatment with the Ti-TADDOLates at higher temperatures. Reactions of (Z)- propenylbenzene 17 and of indene with 2 and 3 give products in moderate enantiomeric purity. Products obtained from reactions of 1-anisylcycloalkenes with 2 differ significantly in yield and enantiomeric purity. In the latter reactions, the ee's of the cyclobutane products are consistently much higher than those of the dihydrobenzofuran products. More significantly, products of different absolute configuration result from different cycloalkenes. With 1- anisylcyclopentene or 1-anisylcyclohexene, all of the products are of similar configuration and are obtained in comparable yields and ee's. However, 1- anisylcycloheptene affords products that are diastereomeric with those of the 1-anisylcyclopentene, and in lower ee's. A mechanistic model is proposed. Application of these reactions to the enantioselective synthesis of the pterocarpan class of isoflavonoid natural products is also reported.

Stereospecific Lewis Acid-Promoted Reactions of Styrenyl Systems with 2-Alkoxy-(6-alkyl)-1,4-benzoquinones: Scope, Limitations, and Synthetic Applications

Titanium(IV)-promoted reactions of various (E)-1-propenylbenzenes with 2-methoxy- and 2-methoxy-6-methyl-1,4-benzoquinones produce trans 2-aryl-6-methoxy-3-(and 4-di)methyl-2,3-dihydro-5-benzofuranols (10-12), rel-(1S,6R,7R,8R)-3-methoxy-8-aryl-7-(and 1-di)methylbicyclooct-3-ene-2,5-diones (2 + 2 cycloadducts, 13-15) and/or rel-(1R,5R,6R,7R)-7-aryl-3-hydroxy-6-(and 4)-methylbicyclooct-3-ene-2,8-diones (5 + 2 cycloadducts, 16/17).In many cases, each of the three products can be obtained selectively in good yield by control of reaction conditions and/or by choice of substituents on the quinone or the propenylbenzene.The dihydrobenzofurans are formed stereoselectively, whereas the formation of the bicyclo systems are stereospecific processes.Thus, reactions of (Z)-1-propenylbenzenes afford rel-(1R,6S,7R,8R)-8-aryl-3-methoxy-7-methylbicyclooct-3-ene-2,5-diones (24, 25).No bicyclosystems are found in reactions of the (Z)-propenylbenzenes.The products all apparently result from a thermally allowed 2? + 4? (2 + 5) cycloaddition of the propenylbenzene with a 2-methoxy-4-oxo-2,5-cyclohexadienyl carbocation intermediate (26) formed by coordination of the Ti(IV) to the C-1 carbonyl oxygen of the quinone.In the cycloaddition, the aryl ring of the propenylbenzene occupies an endo position with respect to the pentadienyl carbocation moiety of 26 and the bicyclo carbocation product of the cycloaddition (28/29) either undergoes dealkylation or rearrangement to yield the observed products.Treatment of the bicylo systems with protic acid effects their rearrangement to the dihydrobenzofuranols.Reactions of 2-propenylbenzenes and arylcycloalkenes with the quinones regioselectively give dihydrobenzofuranols 43-45 and 49-54, respectively; a 2 + 2 cycloadduct is found in low yield in only one case.The 7-aryl-3-hydroxy-6-methylbicyclooct-3-ene-2,8-diones are produced exclusively in reactions of 2-((4-methoxybenzyl)oxy)-1,4-benzoquinones with various propenylbenzenes.Application of these reactions to the synthesis of (+/-)-obtusafuran, (+/-)-liliflol-B, (+/-)-kadsurenone, and (+/-) denudatin are reported.

Selective Control of the Various Cycloaddition Products from Reactions of Styrenes and 1,4-Benzoquinones: Optimization of the Formal 5 +2 Cycloadducts

7-Aryl-3-hydroxy-6-methylbicyclooct-3-ene-2,8-diones 4 and 8 are formed exclusively in Ti(IV)-catalyzed reactions of 2-((4-methoxybenzyl)oxy)-1,4-benzoquinones 5a/d with trans-β-methylstyrene and indene, resprectively.