Acyl and sulfonyl isocyanates in .beta.-lactam synthesis

Abstract

The analytical data of 2a-d and 4a-c are shown in Table IV (supplementary material).Quantum Yield Determination. A solution containing lb or 2b (20-26 mM) in acetonitrile was irradiated with a low-pressure mercury lamp (60 W) under an argon atmosphere through a Coming 9-54 color filter at 20-21 °C. After irradiation, the solvent was evaporated under vacuum and methanol was added to the oily residue. The formed or unreacted Dewar 4-pyrimidinone 2b was converted to the 8-lactam 5.5" Analyses of lb and 5 were performed by HPLC with hexane-CHgC^-CHgCN (92:5:3) as the

Organocatalytic nitrenoid transfer: metal-free selective intermolecular C(sp3)–H amination catalyzed by an iminium salt

“…Flexibility in protecting group choice is a feature of this method that increases its potential utility in synthesis, especially given the relatively harsh conditions required for tosyl deprotection that are inherent in the use of the commonly employed PhINTs. 3 f An investigation of the use of alternative iminoiodinanes revealed that the Tces protecting group, which can be cleaved under milder reductive conditions, 16 is compatible with amination catalysed by 5a . Yields for activated, benzylic, and aliphatic substrates are only modestly lower when PhINTces is used ( Table 3 , products 24–26 ).…”

Preparation, Structure, and Unique Thermal [2+2], [4+2], and [3+2] Cycloaddition Reactions of 4Vinylideneoxazolidin‐2‐one

“…The products 2 q and 2 r form a nice crystalline solid. It should be noted that 2 r was obtained in 28 % overall yield based on 1,1‐dimethylbut‐2‐yn‐1,4‐diol in three‐step assembly‐line operations without purification of the intermediates: moisture and thermal‐sensitive 2,2,2‐trichloroethoxysulfonyl isocyanate16 and biscarbamate 1 r with a propensity to readily undergo polymerization , …”

Phosgene-free synthesis of 1,3-diphenylurea via catalyzed reductive carbonylation of nitrobenzene

“…Moreover, DPU has been extensively studied for application as synthetic intermediates especially for the production of carbamates and isocyanates [9][10][11][12][13][14][15][16][17][18][19][20][21][22], whose importance both in industrial and academic fields is well known. Traditionally, aromatic isocyanates and carbamates are prepared on a commercial scale from aromatic nitro compounds, which are first catalytically hydrogenated to the corresponding amine.…”