Ring synthesis 3-formyl

Acetyl- and 5-formylisothiazoles are readily available from 5-lithioisothiazoles.71,102 However, 3-methyl-4-nitroisothiazole does not form a lithium derivative,72 and 4-formyl-3-methyl-4-nitro-isothiazole was prepared by reduction of the appropriate acid chloride with lithium tri-Lbutoxyaluminum hydride.140 A 5-formyl-4-hydroxy-isothiazole has been prepared by direct ring synthesis [Eq. (12)].29... 

Recently, Vidari et al. synthesized 9-deoxygelsemide (75), which was isolated earlier from Gelsemium elegans by Takayama et al. [104, 105]. The key synthetic steps were the variant Woodward-Prevost reaction for installation of characteristic cis-a-l,2-dioxygenated system at C-6 and C-7, and construction of the dihydropyran ring via formylation of y-lactone. The total synthesis of the iridoid was achieved in 11 steps and 6.6% overall yield from enantiomerically pure lactone (76) (Scheme 97.5). 

The important synthesis of pyrazoles and pyrazolines from aldazines and ketazines belongs to this subsection. Formic acid has often been used to carry out the cyclization (66AHQ6)347) and N-formyl-A -pyrazolines are obtained. The proposed mechanism (70BSF4119) involves the electrocyclic ring closure of the intermediate (587) to the pyrazoline (588 R = H) which subsequently partially isomerizes to the more stable trans isomer (589 R = H) (Section 4.04.2.2.2(vi)). Both isomers are formylated in the final step (R = CHO). 

Acrylic acid, -(3-benzo[f>]thienyl)-a -mercapto-reaction with iodine, 4, 764 Acrylic acid, o -cyano-y3-(2-thienyl)-ring opening, 4, 807 Acrylic acid, -formyl-in pyridazinone synthesis, 3, 46 Acrylic acid, furyl-rotamers, 4, 545 synthesis, 4, 658 Acrylic acid, 2-hydroxybenzoyl-chroman-4-one synthesis from, 3, 850 Acrylic acid, 5-(l-propynyl)-2-thienyl-methyl ester occurrence, 4, 909 Acrylonitrile... 

Isoxazole, 5-(p-anisyl)-3-phenyI-synthesis, 6, 63 Isoxazole, 4-aroyl-3,5-diaryI-synthesis, 6, 71 Isoxazole, aryl-UV spectra, 6, 4 Isoxazole, 3-aryl-5-unsubstituted ring cleavage, 6, 30 Isoxazole, 5-aryl-3-chloro-reactions, 5, 104 Isoxazole, 3-aryI-4-formyl-synthesis, 6, 84 Isoxazole, 3-aryl-5-methoxy-thermal isomerization, 6, 15 Isoxazole, 3-aryl-5-methyl-synthesis, 6, 63, 84 Isoxazole, 4-azorearrangement, 5, 719... 

Thiophene, 2-amino-3-cyano-5-phenyl-synthesis, 4, 888-889 Thiophene, 3-amino-4,5-dihydro-cycloaddition reactions, 4, 848 Thiophene, 2-amino-3-ethoxycarbonyl-ring opening, 4, 73 Thiophene, 2-amino-5-methyl-synthesis, 4, 73 Thiophene, 2-anilino-synthesis, 4, 923-924 Thiophene, aryl-synthesis, 4, 836, 914-916 Thiophene, 2-(arylamino)-3-nitro-synthesis, 4, 892 Thiophene, azido-nitrenes, 4, 818-820 reactions, 4, 818-820 thermal fragmentation, 4, 819-820 Thiophene, 3-azido-4-formyl-reactions... 

It has been shown that acetamidothiophenes 22 can be converted to either chlorothieno[2,3-h]pyridines 23 or chlorothieno[2,3-h]pyridinecarboxaldehydes 24 using POCI3 and DMF by appropriate choice of reaction conditions. However, unlike the acetanilides, initial ring formylation rather than side-chain formylation is believed to lead to the formation of the pyridine ring. These reactions have been extended to the synthesis of the isomeric thieno[3,2-I>]- and thieno[3,4-I>]pyridines, 25 and 26, from 3-acetamidothiophene and 3-acetamido-2,5-dimethylthiophene, respectively. 

This procedure illustrates formylation by N,N-dimethylamino-methoxymethylium methyl sulfate, a compound which can be produced readily by reaction of easily available materials. 6-(Dimethylamino)fulvene is a useful intermediate for the synthesis of various f used-ring nonbenzenoid aromatic compounds. 

Related redox transformations allow the conversion of ynals to a,P-nnsaturated esters [33], as well as the ring expansion of formyl P-lactams [34], oxacycloalkane-2-carboxaldehydes [35], and 2-acyl-1-formyIcyclopropanes [36], Farther developments allow the synthesis of amides from a range of a-fnnctionalised compounds, but require an additive (imidazole, HO At or HOBt) for efficient amidation [37],... 

A major advantage of the sequence presented here is that the aldehyde group is protected at the siloxycyclopropane stage, which allows convenient storage of this stable intermediate. Of equal importance is the valuable carbanion chemistry that can be carried out a to the ester function. Efficient substitution can be achieved by deprotonation with LDA and subsequent reaction with electrophiles.12-13-6 This process makes several a-substituted [1-formyl esters available. Other ring opening variants of siloxycyclopropanes - mostly as one-pot-procedures - are contained in Scheme I. They underscore the high versatility of these intermediates for the synthesis of valuable compounds.6 Chiral formyl esters (see Table, entries 2-5) are of special... 

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