M. Venkat Ram Reddy

A facile synthesis of chiral ω-allyl- and ω-n-propyllactones via asymmetric allylboration of formyl esters with B- allyldiisopinocampheylborane

Abstract Asymmetric allylboration of aldehydes containing an adjacent ester group with B -allyldiisopinocampheylborane, followed by hydrolysis and cyclization, provides the corresponding allyl substituted lactones in high yields and ≥92% enantiomeric excess. Hydrogenation of these lactones provides the corresponding propyl substituted lactones without any loss of optical purity.

VINYLALUMINATION OF FLUORO-CARBONYL COMPOUNDS

Abstract Ethyl acrylate and acrylonitrile fail to undergo efficient Baylis-Hillman reaction with fluoral, but provide good yields of products with pentafluorobenzaldehyde. Alternately, unsubstituted and β-substituted [α-(ethoxycarbonyl)vinyl]aluminum react with perfluoroalkyl and -aryl aldehydes and ketones to provide the α-hydroxyalkenylated fluoro-organic compounds in good to excellent yields.

VINYLALUMINATION OF ACTIVATED CARBONYL COMPOUNDS

Abstract [α-(Ethoxycarbonyl)vinyl]diisobutylaluminum and its β-methyl and -phenyl analogs react with activated ketones, such as α-keto esters, α-acyl cyanides, and α-acetylenic ketones to provide the corresponding α-hydroxyalkenylated products in high yields.

Stereoselective synthesis of the C7C21 segment of epothilone A via asymmetric alkoxyallyl- and crotylboration ☆

The synthesis of the C7C21 fragment of epothilone A involving asymmetric alkoxyallyl- and crotylboration using α-pinene-derived reagents is described.

1,4-diazabicyclo[2.2.2]octane-catalyzed self- and cross-condensation of α-acetylenic ketones

Abstract 3-Butyn-2-one condenses with itself in the presence of 0.1 molar equiv of Dabco providing 80% yield of E -3-(1-buten-3-yn-2-oxy)-buten-2-one. Substitution at the acetylene terminus prevents the condensation. However, such ketones can be condensed with terminal acetylenic ketones to provide the cross-coupled products in high yields.

Tandem allylboration-ring-closing metathesis reactions for the preparation of biologically active molecules*

The development of asymmetric synthesis during the past two decades aided organic chemists considerably in the synthesis of complex natural products. Organoborane chemistry continues to play an important role in asymmetric synthesis. One of the important reactions that has become very common in the arsenal of synthetic chemists is allylboration and related reactions. Another important reaction that has recently attained enormous importance in organic chemistry is the ring-closing metathesis (RCM) reaction. Indeed, a combination of allylboration and RCM reactions provides an excellent route to cyclic ethers, lactones, lactams, etc. Herein, we describe a sequential asymmetric allylboration and RCM reaction protocol that has been utilized for the synthesis of several alpha-pyrone-containing natural products,particularly biologically active molecules.

An improved vinylalumination procedure replacing HMPA with NMO for the hydroalumination of α-acetylenic esters and ketones

Replacing carcinogenic HMPA with NMO, a higher yielding, enviornmentally benign procedure for the vinylalumination of carbonyl compounds with [α-(ethoxycarbonyl)- vinyl]diisobutylaluminium and its β-methyl or -phenyl analogs, as well as [α-(acetyl)vinyl]diisobutylaluminium has been developed.

Carbonyl and olefin reactivities for the Baylis–Hillman reaction of fluorocarbonyls

The product formation and yields for the Baylis–Hillman reaction of fluorine-containing carbonyl compounds depend on a balance between the reactivities of the carbonyl and olefin partners.