Michael-Dieckmann cyclization

Staunton-Weinreb aimulation toward the synthesis of pigmentosin A (Scheme 11). Unfortunately, this one-step procedure using 44d provided poor yields of the naphthopyranone (<40%). After unsuccessful attempts to optimize the reaction, we turned our efforts to a two-step procedure of Michael-Dieckmann cyclization followed by oxidative aromatization. The lithium enolate of 43 reacted with all of our lactones to provide the corresponding desired naphthopyranones after oxidative aromatization with... 

Michael addition of methyl 3-mercaptopropanoate to methyl 3-methylbut-2-enoate and Dieckmann cyclization of the resulting diester yields 2,2-dimethyltetrahydrothiopyran-4-one 539 (Scheme 220) <2005HCA1922>. Similarly, diethyl thiodipropanoate, accessible from ethyl propenoate by treatment with NaSH in methanol, cyclizes to ethyl 4-oxotetrahydrothiopyran-3-carboxylate under basic conditions. The carbon skeleton has also been provided by 1,4-pentadienones <1995JOC1665> and H2S in ethanol has been used as an alternative source of the heteroatom (Scheme 221) <1999SL735>. 

Claisen condensation reaction Dieckmann cyclization Michael reaction Michael acceptor... 

Cyclizations. Cyclization of hydroxylated propargyl sulfones may involve isomerization to the corresponding allenyl sulfones which should behave as Michael acceptors. Access to the indolizidine skeleton by an intramolecular Michael reaction of 5-tosyl-4-pentenamide and subsequent alkylation at nitrogen and carbon is quite efficient. A synthesis of resorcinols from dimethyl acetonedicarboxylate and alkyl alkynoates involves a Michael reaction-Dieckmann cyclization sequence. 

Cyclohexanone-2-carboxylic esters. The reagent acts as a condensation catalyst for twofold Michael additon of a donor to an acrylate ester and Dieckmann cyclization of the 1 2 adducts. However, NaOMe has the same capability therefore, Na2pe(CO)4 is not unique. 

Cyclization by tandem Michael-Dieckmann reaction. Ring construction from compounds with juxtaposed ketone (or ester) and conjugated ester groups is made easy. It is rendered irreversible by trapping the alkoxide ion as a trimethyl-silyl ether. 

N,N-Dichlorurethan as pseudohalogen 24, 563 N,N-Dichlorurethans, addition to 1,3-dienes 24, 554 NjN -(Dicyan)amidines 24, 360 Dicyclohexylcarbodiimide as reagent 24,181 Di(cyclopentadienyl)metal compounds s. Metallocenes Dieckmann cyclization (s. a. under Michael addition)... 

N-Condensed 3-pyrrolidone ring synthesis Michael addition combined with Dieckmann cyclization Subsequent -decarbalkoxylation... 

Preparative Methods prepared by Dieckmann reaction of the Michael adduct of methyl thioglycolate and methyl acrylate. Careful choice of the reaction conditions (MeONa, toluene, 80-120 ° C) and a suitable workup procedure are recommended in order to control the direction of the cyclization which, in principle, can produce both 3-oxo-2-carboxylate and 4-oxo-3-carboxylate isomers. A more sophisticated method to accomplish a direction-controlled Dieckmann cyclization leading to exclusive formation of the target compound as the ethyl ester [78647-31-1] requires the less common ethoxy-carbonylethyl thioethoxycarbonylmethyl sulfide as the starting material. ... 

Dieckmann cyclization, 919 Michael reaction, 921 Robinson annulation reaction, 927 Stork reaction, 925... 

Michael addition combined with Dieckmann cyclization O... 

Key Mechanism 22-12 The Claisen Ester Condensation 1071 22-13 The Dieckmann Condensation A Claisen Cyclization 1074 22-14 Crossed Claisen Condensations 1074 22-15 Syntheses Using /3-Dicarbonyl Compounds 1077 22-16 The Malonic Ester Synthesis 1079 22-17 The Acetoacetic Ester Synthesis 1082 22-18 Conjugate Additions The Michael Reaction 1085 Mechanism 22-13 1,2-Addition and 1,4-Addition (Conjugate Addition) 1085... 

The diester enantiomer (108) derived from ribonolactone, has been cyclized and decarboxylated to the bicyclic ketone (109) in 83% overall yield for the two steps (Scheme 38)." Similarly, the cyclopentanol diester (110) has been cyclized and decarboxylated to (111), separation of the two diastereomers being effected on the deprotected alcohols (Scheme 39)." Cyclization of (112) occurs regioselectively as expected to give (113) in 81% yield (equation 32)." The 9-azaprostaglandin skeleton has been formed through a combination of Michael and Dieckmann reactions." ... 

The cyclization reactions described in this chapter and, occasionally, even the acyclic condensation reactions, can often be prefaced by a different type of process such as a Michael reaction. We shall term such a sequence a tandem reaction and a number of these have already been described. Others will be collected here to illustrate the types of processes that have been observed. The cycloenones (198), when treated with a nucleophile (199) under basic conditions, react in a Michael fashion to give the intermediates (200), which then undergo the Dieckmann reaction to give the bicyclic dione (201). Similarly, methyl cinnamate (202) reacts with the nucleophile (203) in the same tandem sequence to give the cyclopentanone (204) as a diastereomeric mixture (Scheme 89). ... 

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