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An efficient and scalable enone-promoted method for the decarboxylation of trans-4-hydroxy-proline has been developed in flow to provide access to (R)-pyrrolidin-3-ol hydrochloride using biomass-derived isophorone. The advantages of deploying flow in this setting were reinforced by direct comparsion to batch. This method lays a foundation for fossil fuel and ammonia free alternative access to amines on scales relevant to manufacturing.

Singlet nucleophilic carbenes (SNCs) containing only one heteroatom donor remain underutilized in chemical synthesis. We recently discovered that visible-light-induced SNC intermediates can be trapped by fluorinated ketones via 1,2-carbonyl addition to afford benzoin-type products. This discovery represents a rare example of nucleophilic carbenes reacting with ketones and delivers an efficient, user-friendly, and scalable process for accessing fluorinated tertiary alcohol derivatives driven only by light circumventing the use of exogenous catalysts or additives.

Singlet nucleophilic carbenes (SNCs) that contain only one heteroatom donor remain underexplored and underutilized in chemical synthesis. To discover new synthetic strategies that harness these SNCs as reactive intermediates, aromatic or aliphatic siloxy carbenes represent excellent model substrates as they can be readily generated photochemically from stable acyl silane precursors. We herein report the discovery that photochemically generated siloxy carbenes undergo 1,2-carbonyl addition to trifluoromethyl ketones, followed by a silyl transfer process to afford benzoin-type products. This new transformation is a rare example of the use of ketones as trapping reagents for SNC intermediates and delivers an efficient, user-friendly and scalable process to access fluorinated tertiary alcohol derivatives driven by only light, circumventing the use of catalysts or additives.

The combination of multistage mass spectrometry experiments employing the distonic radical approach together with DFT calculations are used to examine addition of the N-methyl-pyridinium-4-yl radical cation (γ-NMP) to iso(thio)cyanates in the gas-phase. The type of products formed depend on the nature of the iso(thio)cyanate: (1) hydrogen atom abstraction occurs for alkyl isocyanates; (2) aryl isocyanates undergo radical-ipso substitution; (3) radical attack occurs at the C[double bond, length as m-dash]C bond of allyl isocyanate; (4) radical attack occurs at the C[double bond, length as m-dash]S bond of isothiocyanates to generate S adducts of γ-NMP and isonitriles. DFT calculations provide insight into the reactivity differences of these heterocumulenes towards the electrophilic C-centered γ-distonic radical cations. Translation of these gas phase results to the solution phase were hampered by dominating radical recombination reactions which appear to be favoured over the radical-iso(thio)cyanate reactions.

The chemoselective reduction of diaryl imines in the presence of competitively reducible groups is uniquely accessed through precise control of reaction and irradiation time by continuous flow visible light photoredox catalysis. The method enables the mild and efficient transfer hydrogenation of diaryl imines in the presence of sensitive functionality including halides, ester, ketone, and cyano groups. The flow protocol is efficient, rapid (>98% conversion within 9 min) and readily scaled to deliver multigram quantities of amine products in high purity.