Acyclic enol phosphates

The coupling reaction between lithium dimethylcuprate and acyclic enol phosphates must be carried out between -47 and -98 C for stereoselective formation of g-methyl-a,g-unsaturated esters. 

The formation of g-alkyl-a,g-unsaturated esters by reaction of lithium dialkylcuprates or Grignard reagents in the presence of copper(I) iodide, with g-phenylthio-, > g-acetoxy-g-chloro-, and g-phosphoryloxy-a,g-unsaturated esters has been reported. The principal advantage of the enol phosphate method is the ease and efficiency with which these compounds may be prepared from g-keto esters. A wide variety of cyclic and acyclic g-alkyl-a,g-unsaturated esters has been synthesized from the corresponding g-keto esters. However, the method is limited to primary dialkylcuprates. Acyclic g-keto esters afford (Zl-enol phosphates which undergo stereoselective substitution with lithium dialkylcuprates with predominant retention of stereochemistry (usually > 85-98i )). It is essential that the cuprate coupling reaction of the acyclic enol phosphates be carried out at lower temperatures (-47 to -9a°C) to achieve high stereoselectivity. When combined with they-... 

ACRYLIC ACID, 2-(BROMOMETHYL)-, METHYL ESTER [4224-69-5], 61, 77 Acyclic enol phosphates, 62, 19... 

The same SN2 addition is also observed in reactions of the cuprate with the silyl enol ether or the enol phosphate of the epoxy ketone. This regiosclectivity is applicable to five- and six-membered ring systems and, to a lesser extent, to acyclic systems, which are generally less reactive. 

A convenient enantioselective catalytic oxidation of a variety of differently substituted, cyclic (E) and acyclic (Z)-enol phosphates with (salen)manganese(III) complex has been reported. The influence of electronic and steric effects of the enol phosphate substituents on the stereoselectivity of oxidation has been studied.50... 

There have appeared several studies on the conformation of acyclic phos-phonic and phosphinic esters and some calculations on the equilibrium conformation of a series of enol phosphates have been reported.Crystal structure determinations on the very reactive cyclic phosphate (1 R = MeO) have shown that the five-membered ring is almost planar and that the carbonyl bond is short. 

New strategies for the synthesis of 2-substituted indoles and indolines (101) using acyclic, imide-derived enol phosphates (100), which were readily prepared from o-haloanilides, have been developed based on Suzuki-Miyaura coupling-cyclization sequences by Fuwa and Sasaki (Scheme 22)." ... 

The asymmetric oxidation of a variety of differently substituted, acyclic and cyclic enol phosphates using the Sharpless AD (asymmetric dihydroxylation)-reagents, AD-mix-a and AD-mix- 0, and a fructose-derived chiral ketone as a catalyst, with PMS was a terminal oxidant, afforded the corresponding a-hydroxy ketones in good yield and with high enantioselectivity. The influence of substrate steric and electronic factors on the facial stereoselectivity has been studied. Kinetic and activation parameters for copper(II)-catalysed and -uncatalysed oxidation of ornithine with PMS have been determined. Cyclic voltammetric and absorption studies confirmed the formation of a copper-ornithine-PMS complex and ESR spectral studies ruled out the participation of free radical intermediates. Kinetic and activation parameters for the oxidation of aspartic acid and nicotinic acid with PMS have been determined and plausible mechanisms have been proposed. 

P-Ketophosphonates are valuable intermediates in the realm of Homer-Emmons alkenation methodology. Acyclic variants are difficult to obtain from enol phosphates due to competing alkyne and allene formation. One solution utilized the dianion derived from a-bromo ketones and trapping with diethyl phosphorochloridate however, only moderate yields of P-keto phosphonates were reported. The most efficient procedure utilizes the anion derived from dialkyl methylphosphonate, addition to an aldehyde, followed by oxidation (eq 8). ... 

The asymmetric oxidation of a variety of acyclic (89) and cyclic (90) substituted enol phosphates using commercially available Sharpless reagent (93), and a fructose derived chiral (94) as a catalyst, afforded the corresponding a-hydroxy ketones (91) and (92) in high enantioselectivily and good yields (Scheme 30). The influence of steric and electronic... 

In 2001, Funk reported a synthesis of ( )-FR901483 using an approach very different from those described previously, taking advantage of his amidoacrolein cycloaddition methodology to prepare 1 -alkyl-1 -aminocyclohexane derivatives, starting the synthesis from acyclic compounds. Moreover, Funk neither uses tyrosine derivatives nor needs an inversion at C(9) to install the phosphate unit. In Funk s retro synthetic analysis, shown in Scheme 23, he envisaged that lactam 60 possessed the necessary functionality for the introduction of the C(6) p-methoxy benzyl and C(3) methylamino substituents via enolate alkylation and amination reactions, respectively. 

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