Rearrangements of Acyl, Thioacyl, and Imidoyl (Thio)cyanates to Iso(thio)cyanates, Acyl Iso(thio)cyanates to (Thio)acyl Isocyanates, and Imidoyl Iso(thio)cyanates to (Thio)acyl Carbodiimides, RCX-YCN reversible arrow RCX-NCY reversible arrow RCY-NCX rever

Koch, Rainer and Wentrup, Curt (2013) Rearrangements of Acyl, Thioacyl, and Imidoyl (Thio)cyanates to Iso(thio)cyanates, Acyl Iso(thio)cyanates to (Thio)acyl Isocyanates, and Imidoyl Iso(thio)cyanates to (Thio)acyl Carbodiimides, RCX-YCN reversible arrow RCX-NCY reversible arrow RCY-NCX reversible arrow RCY-XCN (X and Y = O, S, NR'). Journal of Organic Chemistry, 78 5: 1802-1810. doi:10.1021/jo3013786


Author Koch, Rainer
Wentrup, Curt
Title Rearrangements of Acyl, Thioacyl, and Imidoyl (Thio)cyanates to Iso(thio)cyanates, Acyl Iso(thio)cyanates to (Thio)acyl Isocyanates, and Imidoyl Iso(thio)cyanates to (Thio)acyl Carbodiimides, RCX-YCN reversible arrow RCX-NCY reversible arrow RCY-NCX reversible arrow RCY-XCN (X and Y = O, S, NR')
Journal name Journal of Organic Chemistry   Check publisher's open access policy
ISSN 0022-3263
1520-6904
Publication date 2013-03
Year available 2012
Sub-type Article (original research)
DOI 10.1021/jo3013786
Volume 78
Issue 5
Start page 1802
End page 1810
Total pages 9
Place of publication Washington, DC, United States
Publisher American Chemical Society
Collection year 2013
Language eng
Abstract Two types of rearrangements have been investigated computationally at the B3LYP/6-311+G(d,p) level. The activation barriers for rearrangement of acyl thiocyanates RCO-SCN to the corresponding isothiocyanates RCO-NCS are 30-31 kcal/mol in agreement with the observation that the thiocyanates are in some cases isolable albeit very sensitive compounds. Alkoxycarbonyl-, (alkylthio)carbonyl- and carbamoyl thiocyanates are isolable and have higher calculated barriers (ca. 40 kcal/mol) toward rearrangement to isothiocyanates, whereas all thioacyl thiocyanate derivatives are rather unstable compounds with barriers in the range 20-30 kcal/mol for rearrangement to the isothiocyanates. Acyl-, alkoxycarbonyl-, and carbamoyl cyanates R-CO-OCN are predicted to be in some cases isolable compounds with barriers up to ca. 40 kcal/mol for rearrangement to the isocyanates RCO-NCO. All of the rearrangements of this type involve the HOMO of a nearly linear (thio)cyanate anion and the LUMO of the acyl cation, in particular the acyl =X π* orbital. The second type of rearrangement involves 1,3-shifts of the groups R attached to the (thio)acyl groups, that is, acyl isothiocyanate-thioacyl isocyanate and imidoyl isothiocyanate-thioacyl carbodiimide rearrangements. These reactions involve four-membered cyclic, zwitterionic transition states facilitated by lone pair-LUMO interactions between the migrating R group and the neighboring iso(thio)cyanate function. Combination of the two rearrangements leads to the general reaction scheme RCX-YCN ⇌ RCX-NCY ⇌ RCY-NCX ⇌ RCY-XCN (X and Y = O, S, NR′).
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published: 6 September 2012.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
School of Chemistry and Molecular Biosciences
 
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Created: Fri, 12 Apr 2013, 11:02:28 EST by Mrs Louise Nimwegen on behalf of School of Chemistry & Molecular Biosciences