The intramolecular, stereoselective addition of sulfoximine carbanions to electron deficient alkenes

Abstract only availableChiral Benzothiazine play important roles in synthetic organic chemistry since they can be used in the preparation of enantiomerically pure compounds. We have studied the synthesis of these species using the intramolecular, stereo selective addition of sulfoximine carbanions to general electron deficient alkenes. Details on the synthesis of starting material and cyclization reaction will be presented.Stevens' Chemistry Progra

Highly Regio- and Stereoselective Diels-Alder Cycloadditions via Two-Step and Multicomponent Reactions Promoted by Infrared Irradiation under Solvent-Free Conditions

Infrared irradiation promoted the Diels-Alder cycloadditions of exo-2-oxazolidinone dienes 1–3 with the Knoevenagel adducts 4–6, as dienophiles, leading to the synthesis of new 3,5-diphenyltetrahydrobenzo[d]oxazol-2-one derivatives (7, 9, 11 and 13–17), under solvent-free conditions. These cycloadditions were performed with good regio- and stereoselectivity, favoring the para-endo cycloadducts. We also evaluated the one-pot three-component reaction of active methylene compounds 20, benzaldehydes 21 and exo-2-oxazolidinone diene 2 under the same reaction conditions. A cascade Knoevenagel condensation/Diels-Alder cycloaddition reaction was observed, resulting in the final adducts 13–16 in similar yields. These procedures are environmentally benign, because no solvent and no catalyst were employed in these processes. The regioselectivity of these reactions was rationalized by Frontier Molecular Orbital (FMO) calculations

Total synthesis of Vitamin D3 and its analogs via vinyl sulfone chemistry

A general method has been developed for the synthesis of enantiopure six and seven membered A-ring of Vitamin D3 using dimethylsulfonium methylide. A new coupling strategy has been developed for the total synthesis of Vitamin D3 and 19-nor-Vitamin D3 analogs which involves the reaction of A-ring sulfonyl anion with CD-ring allyl chloride and subsequent desulfonylation and concomitant silyl ether deprotection using TBAF. Enantioselective CD-ring synthesis is also achieved from achiral dienyl sulfone

Intramolecular Methylation of an Allyl Sulfone via Lithium Alkoxyaluminate; Application to the Enantioselective Synthesis of the CD Ring of Vitamin D₃

Alcohol-directed intramolecular methylation of an enantiopure allyl sulfone using AlMe₃ provides a <i>trans</i>-hydrindane CD ring alcohol. The substrate <i>cis-</i>CD ring allyl sulfone alcohol is prepared via intramolecular allyl sulfonyl anion addition to aldehyde using Ba(OH)₂

Intramolecular Methylation of an Allyl Sulfone via Lithium Alkoxyaluminate; Application to the Enantioselective Synthesis of the CD Ring of Vitamin D₃

Alcohol-directed intramolecular methylation of an enantiopure allyl sulfone using AlMe₃ provides a <i>trans</i>-hydrindane CD ring alcohol. The substrate <i>cis-</i>CD ring allyl sulfone alcohol is prepared via intramolecular allyl sulfonyl anion addition to aldehyde using Ba(OH)₂

Fluoride-Mediated Elimination of Allyl Sulfones: Application to the Synthesis of a 2,4-Dimethyl-A-ring Vitamin D₃ Analogue

A coupling strategy for the synthesis of 2,4-dimethyl-1α,25­(OH)₂D₃ is achieved which involves methylation of a pro-A ring vinyl sulfone and in situ traping of the allyl sulfonyl anion with a CD ring allyl chloride. TBAF-promoted 1,2-eliminative desulfonylation and concomitant silyl ether deprotection gives the vitamin D₃ analogue