The preparation of ethyl and isopropyl dienol ethers and dienol pivalate esters from Hagemann's ester and its t-butyl analogue, and the reactions of the derived ester dienolates with electrophiles

Baker, MV; Ghitgas, C.; Haynes, Richard K.; Hilliker, Audrey E.; Lynch, Gary J.; Sherwood, G.V.; Yeo, Hwan-Jin

doi:10.1071/ch9842037

Cited by 7 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This interesting result stimulated us to further examine the influence of the R group of the Baylis-Hillman acceptor [C=C-C(O)R] on this reaction. Thus, we synthesized phenyl vinyl ketone (PVK) [ 6 ], phenyl acrylate [ 7 ], and phenyl thioacrylate [ 8 ] as the Baylis-Hillman acceptors and carefully examined the reaction products formed under the traditional Baylis-Hillman reaction conditions.…”

Section: Introductionmentioning

confidence: 99%

Different Reaction Patterns in the Baylis-Hillman Reaction of Aryl Aldehydes with Phenyl Vinyl Ketone, Phenyl Acrylate and Phenyl Thioacrylate

Shi

Jiang

2002

Molecules

View full text Add to dashboard Cite

In the Baylis-Hillman reaction of aryl aldehydes with phenyl vinyl ketone we have observed exclusive formation of diadducts 4, and that the yields of diadduct can reach 80% with increasing amounts of phenyl vinyl ketone. On the other hand, for phenyl acrylate and phenyl thioacrylate, only the normal Baylis-Hillman adduct was obtained. The effects of substituents were also examined and a plausible reaction mechanism is proposed for the formation of compounds 4.

show abstract

Section: Introductionmentioning

confidence: 99%

Different Reaction Patterns in the Baylis-Hillman Reaction of Aryl Aldehydes with Phenyl Vinyl Ketone, Phenyl Acrylate and Phenyl Thioacrylate

Shi

Jiang

2002

Molecules

View full text Add to dashboard Cite

show abstract

“…The actual synthesis began with aldehyde 10 (Scheme ), available in two steps (70%) from commercial Hagemann's ester .…”

mentioning

confidence: 99%

Transannular Diels−Alder Entry into Stemodanes: First Asymmetric Total Synthesis of (+)-Maritimol

2000

View full text Add to dashboard Cite

+)-Maritimol (1), a member of the stemodane diterpenoids (1-3), was isolated 1 from Stemodia maritima L. (Scrophulariaceae) and used as a Caribbean folk medicine for treatment of venereal diseases. It represents a long-standing synthetic challenge 2 with its unique tetracyclic stemodane framework and the construction of its seven chiral centers, particularly the two central, adjacent quaternary carbons at positions 9 and 10. Reported in this contribution is the first asymmetric total synthesis of (+)-maritimol, applying the TADA strategy, developed in our laboratory (Scheme 1). 3aFrom a synthetic point of view, the A.B.C[6.6.5] trans-syncis (TSC) ring system of maritimol correlated well 4a with our previous fundamental TADA model studies, having demonstrated the stereospecific transformation of 14-and 15-membered transcis-cis (TCC) macrocyclic trienes to the respective A.B.C[6.6.6] 4b and [6.6.7] 4c TSC-tricycles. It was also shown that even tetrasubstituted dienophiles were tolerated, particularly when they were activated. 4a,c Moreover, a discovery that a stereogenic center on the macrocycle at the maritimol pro-12 position may induce perfect diastereoface selection in the TADA reaction was also made. 4aRetrosynthetic analysis suggests that tetracycle 4, a central advanced intermediate of stemodanes, 2a is available via TSCtricycle 5 corresponding 4 to macrocycle 6 (Scheme 1). This chiral macrocycle, in turn, can be made in a highly convergent manner, starting from tetrasubstituted cis-dienophile 7. Following an introduction of the requisite asymmetry via (S)-N-amino-2-(methoxymethyl)pyrrolidine (SAMP) 5 hydrazone-based alkylation with Z-1,3-diiodo-propene (8), 6 a Stille coupling 7 with stannane 9 8 delivers the ω-functionalized acyclic -ketoester substrate for macrocyclization.The actual synthesis began with aldehyde 10 (Scheme 2), available in two steps (70%) from commercial Hagemann's ester. 9 NaBH 4 reduction and silyl protection provided tetrasubstituted cis-dienophile 12 (70%), which was selectively hydrolyzed to monoacid 13 (93%) and further transformed into Weinreb amide 14 (89%). 10 Parallel reduction (DIBAL-H) of both carbonyls afforded, after a methanol quench, methoxytetrahydropyran 15, which could be easily transformed to SAMP 5 hydrazone 16 (83%).(1) Hufford, C. D.; Guerrero, R. D.; Doorenbos, N. J. J. Pharm. Sci. 1976, 95, 778-780. (2) For a recent review on the synthesis of stemodane diterpenoids, see: (a) Toyota, M.; Ihara, M. Tetrahedron 1999, 55, 5641-5679. See also: (b) Pearson, A. J.; Fang, X. Scheme 2 a a Reagents: (a) NaBH4, MeOH, >73%. (b) Imidazole, TBS-Cl, 95%. (c) NaOH, THF, 5°C, 96%. (d) Carbonyldiimidazole then Et3N and NH(OMe)Me‚HCl, 89%. (e) DIBALH, CH2Cl2, -78°C then MeOH, 89%. (f) SAMP, PTSA (cat.), PhH, 80°C, 93%. (g) Imidazole, TBDPSCl, 100%. (h) LDA, 0°C then 8, THF, -100°C, 83%. (i) Mgmonoperoxyphthalate, MeOH/Et2O, 98%. (j) Py‚HF, THF then 9, PdCl2‚(MeCN)2, DMF, 52%. (k) (Cl3C)2CO, PPh3, CH2Cl2, -78 to 0°C , 94%. (l) Cs2CO3, CsI, MeCN, 80°C, 75%. (m) TBAF, THF, 87%. (n)...

show abstract

Ethyl 2-Methyl-4-oxo-2-cyclohexene-1-carboxylate

Zibuck¹

2001

Encyclopedia of Reagents for Organic Synthesis

View full text Add to dashboard Cite

The preparation of ethyl and isopropyl dienol ethers and dienol pivalate esters from Hagemann's ester and its t-butyl analogue, and the reactions of the derived ester dienolates with electrophiles

Cited by 7 publications

References 0 publications

Different Reaction Patterns in the Baylis-Hillman Reaction of Aryl Aldehydes with Phenyl Vinyl Ketone, Phenyl Acrylate and Phenyl Thioacrylate

Different Reaction Patterns in the Baylis-Hillman Reaction of Aryl Aldehydes with Phenyl Vinyl Ketone, Phenyl Acrylate and Phenyl Thioacrylate

Transannular Diels−Alder Entry into Stemodanes: First Asymmetric Total Synthesis of (+)-Maritimol

Ethyl 2-Methyl-4-oxo-2-cyclohexene-1-carboxylate

Contact Info

Product

Resources

About