Editing Isocyanate (section)

== Production ==
Isocyanates are usually produced from [[amines]] by [[phosgenation]], i.e. treating with [[phosgene]]:
:{{chem2 | RNH2 + COCl2 -> RNCO  +  2 HCl }}
These reactions proceed via the intermediacy of a [[carbamoyl chloride]] ({{chem2|RNHC(O)Cl}}).  Owing to the hazardous nature of phosgene, the production of isocyanates requires special precautions.<ref name=Ullmann/>  A laboratory-safe variation masks the phosgene as [[oxalyl chloride]].<ref>Smith (2020), ''March's Organic Chemistry'', rxn.&nbsp;16-7.</ref> Also, oxalyl chloride can be used to form [[acyl]] isocyanates from primary [[amide]]s, which phosgene typically dehydrates to [[nitrile]]s instead.{{sfn|Patai|1977a|p=447}}

Another route to isocyanates entails addition of [[isocyanic acid]] to alkenes.  Complementarily, alkyl isocyanates form by displacement reactions involving alkyl halides and alkali metal cyanates.{{sfn|Patai|1977b|pp=619–818}}

[[Aryl]] isocyanates can be synthesized from reductive [[carbonylation]] of [[nitro compound|nitro-]] and [[nitroso]]arenes; a [[palladium]] catalyst is necessary to avoid side-reactions of the [[nitrene]] intermediate.<ref>{{cite journal|doi=10.1007/BF00949595|title=Effect of carbon monoxide pressure, pyridine concentration, and temperature on synthesis of 1-methyl&shy;benzene 2,4-diisocyanate by carbonylation of 2,4-dinitro&shy;toluene|first1=V.&nbsp;I.|last1=Manov-Yuvenskii|first2=B.&nbsp;A.|last2=Redoshkin|id=UDC 542.91:541.12.034:546.262.3-31:547.546|first3=G.&nbsp;P.|last3=Belyaeva|first4=B.&nbsp;K.|last4=Nefedov|orig-date=21 Jan 1980|publisher=Plenum|journal=Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya|volume=3|pages=614–617|date=March 1981}}</ref><ref>{{cite journal|doi=10.1007/BF00951891|title=Synthesis of aromatic diisocyanates by carbonylation of dinitro compounds with carbon monoxide on palladium catalysts|first1=V.&nbsp;I.|last1=Manov-Yuvenskii|first2=B.&nbsp;A.|last2=Redoshkin|id=UDC 542.91:541.128:547.546:546.263.3-31|first3=G.&nbsp;P.|last3=Belyaeva|first4=B.&nbsp;K.|last4=Nefedov|orig-date=13 Oct 1978|publisher=Plenum|journal=Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya|volume=1|pages=133–136|date=January 1980}}</ref>  

Three rearrangement reactions involving nitrenes give isocyanates:
* [[Schmidt reaction]], a reaction where a [[carboxylic acid]] is treated with [[ammonia]] and [[hydrazoic acid]] yielding an isocyanate.
* [[Curtius rearrangement]] degradation of an [[acyl azide]] to an isocyanate and [[nitrogen gas]].
* [[Lossen rearrangement]], the conversion of a [[hydroxamic acid]] to an isocyanate via the formation of an O-[[acyl]], [[sulfonyl]], or [[phosphoryl]] intermediate.

An isocyanate is also the immediate product of the [[Hofmann rearrangement]], but typically hydrolyzes under reaction conditions.<ref>{{Citation |last=Wallis |first=Everett S. |title=The Hofmann Reaction |date=2011 |work=Organic Reactions |pages=267–306 |url=https://onlinelibrary.wiley.com/doi/10.1002/0471264180.or003.07 |access-date=2025-01-21 |publisher=John Wiley & Sons, Ltd |language=en |doi=10.1002/0471264180.or003.07 |isbn=978-0-471-26418-7 |last2=Lane |first2=John F.}}</ref>