Augusto Rodriguez

Intramolecular cyclization of enyne [3]cumulenals

Abstract Enyne [3]cumlenals have been shown to undergo a Bergman cyclization or an intramolecular [2+2] cycloaddition depending on the nature of substituents on the yne carbon. A hydrogen substituted [3]cumulenal is cleanly converted to a naphthalene product while a trimethylsilyl substituted substrate produces a cyclobutene product.

ALKYLATION REACTIONS OF 3-(PHENYLSULFONYL)METHYL SUBSTITUTED CYCLOPENTENONES

Abstract The readily available 2,3-dibromo-1-(phenylsulfonyl)-1-propene (DBP) undergoes facile reaction with several 1,3-dicarbonyl compounds under basic conditions to give (phenylsulfonyl)methyl substituted cyclopentenones. The pendant sulfonyl group at the C3 position of the cyclopentenone ring offers a versatile site for further elaboration via alkylation. These cyclic α-enone systems are easily metallated with sodium hydride, and the resultant carbanion undergoes both bimolecular and intramolecular alkylations. The overall sequence provides a simple and efficient route to functionalized cyclopentenones. The alkylated sulfones were easily desulfonylated upon heating with tri n-butyltin hydride and AIBN in toluene at 110 °C. A novel base-induced transformation was observed using 3-(phenylsulfonyl)methyl-2-(4-iodobutyl)cyclopentenone. Treatment of this compound with one equivalent of NaH in the presence of HMPA afforded 4-methylene-spiro[4.4]non-2-en-1-one. This reaction proceeds by initial γ-alkylation followed by a 1,3-hydrogen shift and subsequent 1,4-elimination of sulfinate anion.

Boron trifluoride catalyzed rearrangement and dehydration of epoxyalkynols

Abstract Epoxyalkynols undergo a rerrangement/dehydration when reacted with boron trifluoride to provide [3]cumulenals and α-hydroxy allenes.

Application of the 2,3-sigmatropic rearrangement of β-sulfonyl acetylenic carbinols toward the synthesis of 1,4-bis(phenylsulfonyl)-1,3-butadienes

Sulfenic esters of β-sulfur substituted acetylenic carbinols undergo 2,3-sigmatropic rearrangement to produce allenylic sulfoxides which were converted to 1,4-bis(phenylsulfonyl)-1,3-dienes or α,β-unsaturated ketones.

The co-oxidation of conjugated enynes. A convenient synthesis of β-sulfoxy acetylenic carbinols

Abstract Several β-sulfoxy substituted acetylenic carbinols were prepared by the addition of thiyl radicals and oxygen to conjugated enynes.

BENZOCYCLOBUTYLDIHYDROOXEPINS VIA INTRAMOLECULAR CYCLOADDITIONS OF ENYNE [3]CUMULENALS

The synthesis of 2-(3-phenyl-1-trimethylsilanyl-9H-8-oxa-benzo[a]cyclobuta[d]cyclohepten-2ylidene)propionaldehyde is described. The strategy applied for the synthesis of this compound involves the [2+2] intramolecular cycloaddition across the internal double bond of a [3]cumulenal. Introduction In spite of the numerous examples of natural products that contain the oxepin ring (1-3), there are only a handful of synthetic procedures to construct this ring (4-6). Given the limited number of synthetic methods for the construction of the dihydrooxepin nucleus, an intramolecular [2+2] cycloaddition strategy involving [3]cumulenes was formulated. Results and Discussion Efforts were focused on the preparation of cumulenal 1 to be used for the synthesis of dihydrooxepin Z, S i M e 3 Me3Si Ρ HO ^ CHO Ο heat CH3