Hydroxyacetals, phthalans, and isobenzofurans therefrom

A general method has been developed for the preparation of acetylenedicarboxylic acid esters and applied to the synthesis of both achiral and chiral esters. Diels-Alder reactions of one of the chiral esters, the bis(methy1 (S)-lactyl) ester, with various types of dienes, such as phenylbutadiene, orthoquinodimethanes, and isobenzofuran, have been investigated. Moderate asymmetric induction was observed in reactions with dienes bearing an a-hydroxyl group. In one case, an unusual solvent-induced reversal of asymmetric induction was observed.

Section: Resultsmentioning

confidence: 99%

Synthesis of acetylenedicarboxylic acid esters and asymmetric Diels–Alder reactions of the bis(methyl (S)-lactyl) ester

Charlton¹,

Chee²,

McColeman³

1995

“…7 Hz), indicating that the methyl group at C-7 was indeed anti to the oxygen bridge. If the C-7 methyl group was syn to the oxygen bridge, the protons H-8 and H-7 would form a 90" dihedral angle, and would therefore show no coupling (34). This stereochemical assignment was also supported by the highly shielded chemical shift of the C-7 methyl doublet (6 0.93) due to the anisotropy of the C -w -1 0 carbon-carbon double bond.…”

Section: Stereochemistry Of the Adductsmentioning

confidence: 89%

“…Distillation of the crude brown oil provided 33 (27% from 3-methyl-2-butenoic acid), bp 40-44"C/ 0.03 Torr (lit. (21) (2-(5-nzethylfury1))-3-methylbutanoate (34) The acyl cyanide 32 (1.82 g, 16.7 mmol) was dissolved in CS2 (60 mL) under Ar and cooled in an ice bath. To this solution was added AICI, (0.56 g, 4.2 mmol), resulting in a gummy precipitate.…”

Section: -Methyl-2-0x0-3-pentenenitrile (32)mentioning

confidence: 99%

The effect of Lewis acids on the intramolecular Diels–Alder reaction of the furan diene

Rogers¹,

Keay²

1992

Self Cite

A general method is described for effecting the intramolecular Diels–Alder reaction of the furan diene in which the side arm connecting the diene to the dienophile contains four carbon atoms. The use of 1.1 equivalents of methylaluminum dichloride at −78 °C for 2–8 h shifts the Diels–Alder equilibrium towards the products and provides the oxatricyclo adducts in good to excellent yield. Catalytic quantities of methylaluminum dichloride (10 mol%) provided a higher quantity of adduct than excess Lewis acid when the enone was substituted with alkyl groups. The scope was extended to include a precursor containing a five carbon atom side arm, and two examples containing acetylenic dienophiles that were activated by a carbonyl moiety on the side arm. Precursors having a four carbon atom side arm provided only oxatricyclo adducts having the side arm syn to the oxygen bridge. The assignment of the stereochemistry of the oxatricyclo adducts is discussed in detail.

“…In general, the bond lengths and angles of the oxabicyclo moieties in l a and l c are comparable to those determined (8) for the furan -maleic anhydride adduct 2. The only significant difference between the two systems is that the C(1)-O(1)-C (4) plane in l a and l c is tilted towards the benzene ring 7.4" more than the corresponding plane is tilted towards the 5,6-double bond in 2 ( For personal use only.…”

Section: Discussionmentioning

confidence: 99%

The crystal structures of 2-endo-acetyl and 2-endo-carbomethoxy-1,4-epoxy-6,7-dimethoxy-1,2,3,4-tetrahydronaphthalenes

Taylor¹,

Keay²,

Rodrigo³

1984

[Traduit par le journal] Introduction In the preceding paper (1) we described two general 5-endo-trig reversals of 7-oxabicyclo[2.2.1] heptenes and heptanes. Our rationalization of these processes as reverse-Michael and reverse-aldol reactions in general violation of Baldwin's rules (2) relied heavily upon the geometry of two benzo derivatives determined by X-ray crystallography. Diels-Alder adducts of isobenzofurans have not been previously subjected to X-ray analysis with the exception (3) of one rather exotic adduct of 1,3-diphenylisobenzofuran. In this paper we report the results of our analyses of the endo isomers of l a and lc.