Microwave-promoted carbonylations

The frequency used by domestic microwave ovens and synthesizers (2.45 GHz, 

2 cm) is located between these extremes where dipoles have time to partly realign with the oscillating electric field but cannot follow the field fluctuations, resulting in an effective heat generation [5,10-12]. 

Microwave-Promoted Carbonylations Using Mo(CO)g as a Source of Carbon Monoxide 

The first example of a microwave-promoted carbonylation was published by Kaiser et al. [13]. In this investigation, the palladium-catalyzed carbonylation of aryl halides 

4-dioxane, and THF) were found superior to DMF, acetonitrile, and toluene and, accordingly, THF was chosen as a suitable solvent. 

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The positive results achieved in developing aminocarbonylation protocols prompted the evaluation of other nucleophiles in similar microwave-promoted carbonylations. Surprisingly, few reports concerning the direct carbonylation of aryl or vinyl halides with hydrazides to the corresponding N,N -diacylhydrazines are found in the literature and an effort was made to modify the previously reported aminocarbonylation protocol [17] for the carbonylative synthesis of N, /-diacylhydrazines [19]. 

Mo(CO)6 has also been used in other types of microwave-promoted carbonylative chemistry. In 2005, Larhed and coworkers presented a carbonylative cyclization protocol whereby ortho-bromo- and ortho-chlorostyrenes were converted into indan-1-ones [21]. Optimized reaction conditions for o-Br-styrenes involved Pd(OAc)2 and 2 as catalytic system with Mo(CO)6 as CO source, n-Bu4NCl as additive and pyridine as base in 1,4-dioxane. Microwave-heating at 150 °C for 30 min provided indanones in 59-82% yield (Scheme 4.5) [21]. 

Microwave-Promoted Carbonylations Using Co2(CO)g as a Reaction Mediator... 

Microwave-Promoted Carbonylations Using Reaction Vessels Prepressurized with Carbon Monoxide... 

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