Carbonate esters are utilized as
solvents and reagents for C1 building
blocks in organic synthesis. This study reports a novel photo-on-demand
in situ synthesis of carbonate esters with CHCl3 solutions
containing a mixture of an aromatic or haloalkyl alcohol having relatively
high acidity, and an organic base. We found that the acid–base
interaction of the alcohol and base in the CHCl3 solution
plays a key role in enabling the photochemical reaction. This reaction
allows practical syntheses of diphenyl carbonate derivatives, haloalkyl
carbonates, and polycarbonates, which are important chemicals and
materials in industry.
Chloroformates are key reagents for synthesizing carbonates and carbamates. The present study reports a novel photo-on-demand in situ synthesis of chloroformates with a CHCl 3 solution containing a primary alkyl alcohol. It further allowed the one-pot synthesis of carbonates and carbamates through subsequent addition of alcohols or amines, respectively.
The Vilsmeier reagent (VR), first reported a century ago, is a versatile reagent in a variety of organic reactions. It is used extensively in formylation reactions. However, the synthesis of VR generally requires highly toxic and corrosive reagents such as POCl 3 , SOCl 2 , or COCl 2 . In this study, we found that VR is readily obtained from a CHCl 3 solution containing N,Ndimethylformamide or N,N-dimethylacetamide upon photoirradiation under O 2 bubbling. The corresponding Vilsmeier reagents were obtained in high yields with the generation of gaseous HCl and CO 2 as byproducts to allow their isolations as crystalline solid products amenable to analysis by X-ray crystallography. With the advantage of using CHCl 3 , which bifunctionally serves as a reactant and a solvent, this photo-on-demand VR synthesis is available for one-pot syntheses of aldehydes, acid chlorides, formates, ketones, esters, and amides.
Chloroform (CHCl 3 ) upon bubbling with O 2 containing ³2% Cl 2 underwent oxidative photochemical conversion to phosgene (COCl 2 ) when exposed to a white LED light. Cl 2 may serve as a visible light-responsive radical initiator in the radical chain reactions of CHCl 3 and O 2 . This photochemical reaction allowed both in situ and stepwise one-pot phosgenation reactions, which are simple and safe methods, without expensive apparatus. It can be applied to a variety of conventional organic syntheses using phosgene and phosgene oligomers.
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