Synthesis of Terpenoids. IV. The Use of Kinetic Enolates of some Methyl Ketones For Terpenoid Syntheses

Park, Oee Sook; Grillasca, Yvonne; Garcı́a, Gustavo; Maldonado, Luis A.

doi:10.1080/00397917708050760

Cited by 14 publications

(4 citation statements)

References 9 publications

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“…160-165 °C /10 mm, (lit. 8,12 (7): To a solution of 3 (2.62 g, 0.01 mol) in dry dichloromethane (20 ml), dry pyridine (1.58 g, 0.02 mol) was added under nitrogen atmosphere and stirred for 0.5 h. 3,3-Dimethylacryloyl chloride (1.20 g, 0.011 mol) in dry dichloromethane (5 ml) was added dropwise with stirring at 0 °C during 30 min and the reaction mixture was stirred in the same ice-bath for 1 h and then at room temperature for 6 h. The contents were poured into water (30 ml) and the organic material was extracted into dichloromethane. The organic extract was washed repeatedly with water, sodium bicarbonate solution, water and dried over anhydrous calcium chloride.…”

Section: -(P-tolyl)ethylmentioning

confidence: 99%

“…The removal of solvent by distillation gave a crude product which was purified by TLC over silica gel (90% pet.ether + 10% ethyl acetate) to furnish a yellow viscous product 7 (2.83 g, 85%). 1 ar-Turmerone (6): The hydrolysis of alkyl-acyl Meldrum's acid (7) or its ethanolysis product (8) was achieved using the following approaches to give 6 in 43-60% yields.…”

Section: -(P-tolyl)ethylmentioning

confidence: 99%

“…After the proposal of structure 6 for arturmerone, 4 it has been synthesised by several methods in good yields. 4,[5][6][7][8][9][10][11][12] The monocyclic sesquiterpene α-curcumene (12) was first isolated 13,14 from the essential oil of rhizomes of Curcuma aromatica Salisb. A large number of essential oils have been shown to contain α-curcumene 15,16 .…”

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Application of Meldrum's Acid in Natural Product Synthesis. Synthesis of Ar-Turmerone and α-Curcumene

Mahulikar

Mane

2006

Journal of Chemical Research

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Section: -(P-tolyl)ethylmentioning

confidence: 99%

Section: -(P-tolyl)ethylmentioning

confidence: 99%

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Application of Meldrum's Acid in Natural Product Synthesis. Synthesis of Ar-Turmerone and α-Curcumene

Mahulikar

Mane

2006

Journal of Chemical Research

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“…Structures of both 2 and 4 were supported by physical data, whose mass spectra, however, were entirely different from natural products, A and B,*** and therefore we turned to synthesize p-ketols, 1 and 3. 6 ) reported the preparation of these compounds, 1 and 3, in order to apply the base * 5b and 5c could be separated by preparative GLC (glass column, SE30, 2 m x 2 cm), ** Since carbanion of 5c bears the adjacent talkyl group, approach of methylvinylketone is stericaUy hindered. Thus 5c was almost quantitatively recovered from the reaction mixture.…”

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Structure and the Synthesis of Novel Constituents of Yudzu Peel Oil and Their Conversion to Related Monoterpenes

Kitahara

Takagi

Matsui

1980

Agricultural and Biological Chemistry

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The Directed Aldol Reaction

1982

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The aldol reaction, usually carried out in protic solvents with base or acid as the catalyst, is one of the most versatile methods in organic synthesis. By application of this reaction a great number of aldols and related compounds have been prepared from various carbonyl compounds. However, because of difficulty in directing the coupling, the conventional method has serious synthetic limitations. This is particularly notable when two different carbonyl compounds are used in a cross‐coupling; the reaction is often accompanied by undesirable side reactions such as self‐condensation and polycondensation. The synthetic limitation arises because the reaction is reversible and cannot be driven to completion if the aldol is less stable than the parent carbonyl compounds. In addition, the reverse reaction, in the presence of acid or base, generates regioisomeric enols or enolates, which in turn attack the carbonyl compounds to yield a mixture of aldols. Furthermore, the aldols are often dehydrated and the resulting unsaturated carbonyl compounds may undergo a Michael addition between enolate anions to give a complex reaction mixture. During the last decade new methods have been developed for the directed coupling of two different carbonyl compounds (or carbonyl equivalents) to give specific carboncarbon bond formation between the α‐carbon atom of one carbonyl compound and the other carbonyl component to produce a desired crossed aldol. These methods provide regiospecific reactions for forming carboncarbon bonds and allow the synthesis of a wide variety of aldols by directed self‐ or cross‐coupling. The success of the reaction depends on effective interception of the aldol‐type adduct by formation of a stable six‐membered chelate. This interception can usually be achieved by reaction of a carbonyl compound with a suitably reactive metal enolate or enol ether that is derived regioselectively from the other carbonyl compound. Reaction of a carbonyl compound with lithium enolates or preformed lithio derivatives of imines is a typical method used for preparation of crossed aldols, even though the reaction is carried out under strongly basic conditions. Use of magnesium, aluminum, or zinc enolates permits rather milder reaction conditions. A clean aldol reaction has been achieved using vinyloxyboranes in a process that is carried out under neutral conditions to produce various crossed aldols in excellent yields. The titanium tetrachloride–promoted coupling of silyl enol ethers, enol ethers, or enol esters with carbonyl compounds, acetals, or ketals is another particularly useful method for the preparation of aldols. The powerful electrophilic activation of the carbonyl acceptor by titanium tetrachloride provides the driving force for this reaction. The acidic reaction medium makes the method useful for compounds that have base‐sensitive functional groups. These directed aldol reactions provide efficient methods for the regiospecific formation of new carboncarbon bonds and can be used for the preparation of key intermediates in the synthesis of important natural products. This chapter includes examples where the coupling reactions are of aldehydes, ketones, or their equivalents.

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Synthesis of Terpenoids. IV. The Use of Kinetic Enolates of some Methyl Ketones For Terpenoid Syntheses

Cited by 14 publications

References 9 publications

Application of Meldrum's Acid in Natural Product Synthesis. Synthesis of Ar-Turmerone and α-Curcumene

Application of Meldrum's Acid in Natural Product Synthesis. Synthesis of Ar-Turmerone and α-Curcumene

Structure and the Synthesis of Novel Constituents of Yudzu Peel Oil and Their Conversion to Related Monoterpenes

The Directed Aldol Reaction

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